add rcmain startup for rc.

maintains window label with current directory in 9term

rcmain

@@ -0,0 +1,37 @@
+# rcmain: Plan 9 on Unix version
+if(~ $#home 0) home=$HOME
+if(~ $#home 0) home=/
+if(~ $#ifs 0) ifs=' 	
+'
+switch($#prompt){
+case 0
+	prompt=('% ' '	')
+case 1
+	prompt=($prompt '	')
+}
+if(~ $rcname ?.out) prompt=('broken! ' '	')
+if(flag p) path=/bin
+if not{
+	finit
+	if(~ $#path 0) . <{/bin/sh -c 'echo $PATH |
+				sed "s/^/path=(''/; s/$/'')/; s/:/'' ''/g"'}
+}
+fn sigexit
+if(! ~ $#cflag 0){
+	if(flag l && /bin/test -r $home/lib/profile) . $home/lib/profile
+	status=''
+	eval $cflag
+}
+if not if(flag i){
+	if(~ $TERM 9term && ~ $#'fn#cd' 0) fn cd { builtin cd $1 && label `{pwd} }
+	if(flag l && /bin/test -r $home/lib/profile) . $home/lib/profile
+	status=''
+	if(! ~ $#* 0) . $*
+	. -i '/dev/stdin'
+}
+if not if(~ $#* 0) . '/dev/stdin'
+if not{
+	status=''
+	. $*
+}
+exit $status