A few fixes to winsup/utils/cygpath.cc

[Jonathan Kamens]

2001-12-26  Jonathan Kamens  <jik@curl.com>

	* cygpath.cc (doit): Detect and warn about an empty path.  Detect
	and warn about errors converting a path.
	(main): Set prog_name correctly -- don't leave an extra slash or
	backslash at the beginning of it.