man: update man pages to say $HOME when accurate

Fixes #386.

man/man1/acid.1

@@ -48,7 +48,7 @@ is a programmable symbolic debugger.
 It can inspect one or more processes that share an address space.
 A program to be debugged may be specified by the process id of
 a running or defunct process,
-or by the name of the program's text file 
+or by the name of the program's text file
 .RB ( a.out
 by default).
 At the prompt,
@@ -63,7 +63,7 @@ Allow the textfile to be modified.
 Print variable renamings at startup.
 .TP
 .BI -l " library
-Load from 
+Load from
 .I library
 at startup; see below.
 .TP
@@ -84,8 +84,8 @@ obtains standard function definitions from the library file
 architecture-dependent functions from
 .BR \*9/acid/$objtype ,
 user-specified functions from
-.BR $home/lib/acid ,
-and further functions from 
+.BR $HOME/lib/acid ,
+and further functions from
 .B -l
 files.
 Definitions in any file may override previously defined functions.
@@ -106,7 +106,7 @@ to create
 .I acid
 functions for examining data structures.
 .SS Language
-Symbols of the program being debugged become integer 
+Symbols of the program being debugged become integer
 variables whose values are addresses.
 Contents of addresses are obtained by indirection.
 Local variables are qualified by
@@ -114,7 +114,7 @@ function name, for example
 .BR main:argv .
 When program symbols conflict with
 .I acid
-words, distinguishing 
+words, distinguishing
 .B $
 signs are prefixed.
 Such renamings are reported at startup; option
@@ -127,7 +127,7 @@ and formats are inferred from assignments.
 Truth values false/true are attributed to zero/nonzero
 integers or floats and to empty/nonempty lists or strings.
 Lists are sequences of expressions surrounded by
-.BR {\^} 
+.BR {\^}
 and separated by commas.
 .PP
 Expressions are much as in C,
@@ -219,7 +219,7 @@ Same as
 .BR spr();gpr() .
 .TP
 .BI fmt( expr , format )
-Expression 
+Expression
 .I expr
 with format given by the character value of expression
 .IR format .
@@ -243,7 +243,7 @@ List current source directories.
 Add a source directory to the list.
 .TP
 .BI filepc( where )
-Convert a string of the form 
+Convert a string of the form
 .IB sourcefile : linenumber
 to a machine address.
 .TP
@@ -288,7 +288,7 @@ interpreted according to a string of format codes.
 .BI dump( address , n , string\fP)
 Like
 .BR mem (),
-repeated for 
+repeated for
 .I n
 consecutive blocks.
 .TP
@@ -300,7 +300,7 @@ Start a new process with arguments given as a string
 and halt at the first instruction.
 .TP
 .B new()
-Like 
+Like
 .IR newproc (),
 but take arguments (except
 .BR argv[0] )
@@ -308,7 +308,7 @@ from string variable
 .BR progargs .
 .TP
 .B win()
-Like 
+Like
 .IR new (),
 but run the process in a separate window.
 .TP
@@ -337,7 +337,7 @@ When a pid or core file is specified on the command line,
 .I acid
 will, as part of its startup, determine the set of shared libraries
 in use by the process image and map those at appropriate locations.
-If 
+If
 .I acid
 is started without a pid or core file
 and is subsequently attached to a process via
@@ -414,7 +414,7 @@ acid: *argv0
 acid: bpset(ls)
 acid: cont()
 70094: breakpoint  ls	ADD	$-0x16c8,R29
-acid: 
+acid:
 .EE
 .PP
 Display elements of a linked list of structures:
@@ -499,7 +499,7 @@ acid: cont()
 .br
 .B \*9/acid/truss
 .br
-.B $home/lib/acid
+.B $HOME/lib/acid
 .SH SOURCE
 .B \*9/src/cmd/acid
 .SH "SEE ALSO"

man/man1/acme.1

@@ -300,7 +300,7 @@ Delete window without checking for dirtiness.
 Write the state of
 .I acme
 to the file name, if specified, or
-.B $home/acme.dump
+.B $HOME/acme.dump
 by default.
 .TP
 .B Edit
@@ -403,7 +403,7 @@ commands named as arguments.
 Restore the state of
 .I acme
 from a file (default
-.BR $home/acme.dump )
+.BR $HOME/acme.dump )
 created by the
 .B Dump
 command.
@@ -745,9 +745,9 @@ and
 .I awd
 reside.
 .SH FILES
-.TF $home/acme.dump
+.TF $HOME/acme.dump
 .TP
-.B $home/acme.dump
+.B $HOME/acme.dump
 default file for
 .B Dump
 and

man/man1/rc.1

@@ -806,6 +806,10 @@ is set to its process id.
 .B $home
 The default directory for
 .BR cd .
+Defaults to
+.B $HOME
+or else
+.LR / .
 .TP
 .B $ifs
 The input field separators used in backquote substitutions.

man/man1/sam.1

@@ -1,7 +1,7 @@
 .TH SAM 1
 .ds a \fR*\ \fP
 .SH NAME
-sam, B, E, sam.save, samterm, samsave \- screen editor with structural regular expressions 
+sam, B, E, sam.save, samterm, samsave \- screen editor with structural regular expressions
 .SH SYNOPSIS
 .B sam
 [
@@ -43,7 +43,7 @@ The options are
 .TP
 .B -a
 Autoindent.  In this mode, when a newline character is typed
-in the terminal interface, 
+in the terminal interface,
 .I samterm
 copies leading white space on the current line to the new line.
 .TP
@@ -121,7 +121,7 @@ is the beginning of the file.
 .TP
 .BI ? regexp ?
 The substring that matches the regular expression,
-found by looking toward the end 
+found by looking toward the end
 .RB ( / )
 or beginning
 .RB ( ? )
@@ -248,7 +248,7 @@ or
 is reversed.
 .PP
 It is an error for a compound address to represent a malformed substring.
-Some useful idioms: 
+Some useful idioms:
 .IB a1 +-
 \%(\f2a1\fB-+\f1)
 selects the line containing
@@ -258,7 +258,7 @@ locates the first match of the expression in the file.
 (The form
 .B 0;//
 sets dot unnecessarily.)
-.BI ./ regexp /// 
+.BI ./ regexp ///
 finds the second following occurrence of the expression,
 and
 .BI .,/ regexp /
@@ -276,7 +276,7 @@ newline may not appear literally;
 .B \en
 may be typed for newline; and
 .B \e/
-quotes the delimiter, here 
+quotes the delimiter, here
 .LR / .
 Backslash is otherwise interpreted literally, except in
 .B s
@@ -284,7 +284,7 @@ commands.
 .PP
 Most commands may be prefixed by an address to indicate their range
 of operation.
-Those that may not are marked with a 
+Those that may not are marked with a
 .L *
 below.
 If a command takes
@@ -347,12 +347,12 @@ Substitute
 .I text
 for the first match to the regular expression in the range.
 Set dot to the modified range.
-In 
+In
 .I text
 the character
 .B &
 stands for the string
-that matched the expression. 
+that matched the expression.
 Backslash behaves as usual unless followed by
 a digit:
 .BI \e d
@@ -500,7 +500,7 @@ Plan 9 command.
 .BI \*acd " directory
 Change working directory.
 If no directory is specified,
-.B $home
+.B $HOME
 is used.
 .PD
 .PP
@@ -543,7 +543,7 @@ For each match of the regular expression in the range, run the command
 with dot set to the match.
 Set dot to the last match.
 If the regular
-expression and its slashes are omitted, 
+expression and its slashes are omitted,
 .L /.*\en/
 is assumed.
 Null string matches potentially occur before every character
@@ -652,7 +652,7 @@ If no address is specified (the
 command is a newline) dot is extended in either direction to
 line boundaries and printed.
 If dot is thereby unchanged, it is set to
-.B .+1 
+.B .+1
 and printed.
 .PD
 .SS Grouping and multiple changes
@@ -713,7 +713,7 @@ of a rectangle.
 from the command window or the whole screen, depending on
 where the null rectangle is.
 .TF resize
-.TP 
+.TP
 .B new
 Create a new, empty file.
 .TP
@@ -819,7 +819,7 @@ typed in a command.
 Send the text in dot, or the snarf buffer if
 dot is the null string, as if it were typed to the command window.
 Saves the sent text in the snarf buffer.
-(Command window only.) 
+(Command window only.)
 .PD
 .SS Simulated buttons
 For systems without a three-button mouse, the keyboard modifier