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

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

Comparing the output of

    nm -D libGL.so.349.16 | grep ' T gl[^X]' | sed 's/.* T //'

between Catalyst NVIDIA 349.16 and this commit, the only change is a bunch
of functions that NVIDIA exports that Mesa does not.

If a function is not statically exported by either of the major binary
drivers on Linux, there is almost zero chance that any application
statically links with it.

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