piglit: fix building issues regarding gbm_bo_map and a MESA test
These patches fix a few building problems but are not being
taken into consideration at the moment, even though they have
been reviewed upstream with most of them merged (and accepted
already in OE-core master):
1.- CMake: define GBM_BO_MAP only when symbol is found
2.- util/egl: Honour Surfaceless MESA in get_default_display
3.- egl_mesa_platform_surfaceless: Don't use eglGetPlatformDisplay directly
4.- egl_mesa_platform_surfaceless: Use EXT functions for surfaces
Signed-off-by: Daniel Díaz <daniel.diaz@linaro.org> Signed-off-by: Ross Burton <ross.burton@intel.com>
