glapi: Remove static dispatch for functions that didn't exist in 10.5

glapi: Remove static dispatch for functions that didn't exist in 10.5

Comparing the output of

    nm libGL.so | grep ' T gl[^X]' | sed 's/.* T //'

between 10.5.5 and this commit, the only change is the removal of
glFramebufferTextureFaceARB.  This function was removed a couple commits
previously.

None of these functions are particuarly new.  If applications were not
statically linking them with 10.5.5, there's approximately zero chance
they will for 10.6.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>