MUSTCOPY seems to have only been defined in <X11/Xmd.h> when building for
CRAY, to handle missing some sizes of integer type.

(mostly performed with unifdef, followed by some manual cleanup of
 spacing/indenting in the remaining code)

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>