Possible path processing change

["Parker, Ron" <rdparker at butlermfg dot com>]

This originally started as an idea for fixing some of the differences
between how UNIX and cygwin handle paths.

Currently cygwin recognizes both /cygdrive/<drive-letter> and
//<drive-letter> as paths for unmounted drives.  Additionally it recognizes
//server/share as a UNC path.  This leads to two problems.  The first is
that //<drive-letter>/directory can be ambiguous.  The second is that
scripts and programs which build paths beginning with two slashes do not
resolve to absolute paths under cygwin as they do in UNIX.

This lead to a few ideas:
* Remove support for //<drive-letter>
* Replace //server/share with server:share
* Replace //*path with /path

This would get rid of the ambiguity of double-slashed paths and allow cygwin
to handle sloppy programs that try to access //path, ///path and similar
things.

Chris has already requested the //server/share stay in place because of a
number of scripts that he has.  Prior to his request I thought these changes
might speed up path conversion.  Now I am not sure.

Would any of these things be worth doing?

If there is no //server/share should we try parsing it as /directory/...?