xutil_util-macros: move outside x11r7 scope

Move to baseline package/
It doesn't really require x11r7 infrastructure and is in fact needed by
libepoxy which can be made x11r7-less.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>