(find_app_on_path): Use SYMLINK_MAX. Resolve symlink relative
to link's location. Adjust to the fact that cygpath already
normalizes its return value.
* path.cc (rel_vconcat): Add cwd parameter, and use it instead
of calling GetCurrentDirectory() if possible. Rename throughout.
(vcygpath): Rename from cygpath and accept cwd and va_list. Pass
cwd on to rel_vconcat().
(cygpath_rel): New front end for vcygpath.
(cygpath): Ditto.
* path.h (cygpath_rel): Declare.
(SYMLINK_MAX): Define to 4095.