xlib_libxshmfence: New package

Needed for DRI3 support in mesa3d:

configure: error: Package requirements (x11 xext xdamage xfixes x11-xcb xcb-glx >= 1.8.1
 xcb-dri2 >= 1.8 xcb-dri3 xcb-present xcb-sync xshmfence >= 1.1) were not met:

Package xshmfence was not found in the pkg-config search path.

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