_mesa_create_exec_table: de-deprecate GetPointerv.

_mesa_create_exec_table: de-deprecate GetPointerv.

glGetPointerv was de-deprecated in GL 4.3, because GL 4.3 adds
functionality from KHR_debug and ARB_debug_output, which require
glGetPointerv.

This patch modifies _mesa_create_exec_table() to populate
glGetPointerv in the dispatch table for core contexts.

Technically this is not in compliance with the spec--what we really
ought to do for core contexts is expose glGetPointerv only when a GL
4.3 context is in use or one of the two extensions is present.
However, it seems silly to go to that extra work, since the only
client-visible effect would be for glGetPointerv to raise an
INVALID_OPERATION error instead of an INVALID_ENUM error.  Besides,
the other functions set up by _mesa_create_exec_table() only depend on
the API in use, not on the GL version or extensions supported.

Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>