git push #1

For anyone interested in the git repository, I just pushed my first
commit with

	git push ssh://[email protected]/freetds/freetds.git

It seemed work.  I'm still getting the hang of git.  

There are two changes:

1.  fix code that induces warnings in clang.  All innocuous.  
2.  remove txt2man.

All man pages are now in -mdoc format.  It was a few hours' work.  The
man pages now look a little better and we lose one dependency.  With a
little cleverness, we could have them in PDF format, too.  

The warnings were mostly about using // as a comment, something I'm
guilty of.  These became either /**/ or #if 0.  

The most significant changes are to md4.c and md5.c.  Each had a line 

	memset(ctx, 0, sizeof(ctx));
now
	memset(ctx, 0, sizeof(*ctx));	

The line intends to clear memory before returning to prevent sensitive
data from remaining in memory.  It was clearing sizeof(void*) instead of
the whole structure.  

--jkl