package/x11r7/libepoxy: New package

xdriver_xf86-video-ati needs glamor support from xserver_xorg-server,
which in turn depends on libepoxy.

[Thomas: add license information.]

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>