IsModifierKey, defined in include/X11/Xutil.h, is a macro determining,
which keys are regarded as modifiers. The constants ISO_Level5_Shift,
ISO_Level5_Latch and ISO_Level5_Lock where excluded previously, leaving
some Neo2 modifiers functionless in combination with compose.
This patch adjusts the range to include the correct, full range of
modifier constants.

Neo2 Bug 277 <http://wiki.neo-layout.org/ticket/277>

X.Org Bug 21910 <http://bugs.freedesktop.org/show_bug.cgi?id=21910>
Signed-off-by: Bodo Graumann <mail@bodograumann.de>
Reviewed-by: Daniel Stone <daniel@fooishbar.org>
Backported-to-NX-by: Ulrich Sibiller <uli42@gmx.de>