Merge branch 'ml/cygwin-fixes'

Remove some code supporting ancient Cygwin Tcl/Tk versions. Also fix exploring working directory and making desktop shortcuts on Cygwin. * ml/cygwin-fixes: git-gui - use mkshortcut on Cygwin git-gui - use cygstart to browse on Cygwin git-gui - remove obsolete Cygwin specific code git gui Makefile - remove Cygwin modifications