Removed obsolete -m32 and -ivl options from iverilog-vpi man page
and revised description of -mingw option. Also removed duplicate
descriptions of --cflags, --ldflags, and --ldlibs options. Updated
link to main iverilog web page in all man pages.
Try to put all the version stamps into common version_base.h
and version_stamp.h header files. All the source programs then
get their version from these header files.
Also handle the version stamps in the man pages by using the
version_*.h header file contents to edit the version strings
in the man page title bar markers.