include: Stop including <X11/fonts/fontproto.h>

Despite being packaged in xorgproto (formerly fontsproto), fontproto.h
is actually a list of the ABI libXfont version 1 expected of the X
server. We switched to libXfont2 three years ago, this is unnecessary.

Signed-off-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Eric Anholt <eric@anholt.net>