libwayland-egl: fix linkage & no version pinning required

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
initial add libgbm skeleton

based on git://github.com/robclark/libgbm.git
updated with git://anongit.freedesktop.org/mesa/mesa

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
backend_pvr_omap3: code refactoring inspired by mesa gbm dri backend

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>