* cygwin/external.cc (cygwin_internal): Implement CW_SET_DOS_FILE_WARNING.

* cygwin/include/sys/cygwin.h: Define CW_SET_DOS_FILE_WARNING.
* utils/mount.cc (main): Turn dos file warnings off since we know what we're
doing.

winsup/utils/mount.cc

@@ -348,6 +348,8 @@ main (int argc, char **argv)
       exit (1);
     }
 
+  cygwin_internal (CW_SET_DOS_FILE_WARNING, false);
+
   argc--;
   switch (do_what)
     {