The overloading of IR emits magic \X'...' sequences that turn into HTML manual links.
But not all such IR invocations should be manual links;
those had to be written to avoid the IR macro before.
Worse, the \X'...' ending the IR causes troff to emit only a single space after a period.
Defining a new IM macro for manual references fixes both problems.
Fixes#441.
Rename following .cvsignore files to .gitkeep since they are
required by the build (directories must exist before build):
- bin/fossil/.gitkeep
- bin/fs/.gitkeep
- bin/venti/.gitkeep
Change-Id: I9c2865058480cffb3a4613f25e2eca1f7e5578c0
