glapi: gl_table.py: replace getopt with argparse.

glapi: gl_table.py: replace getopt with argparse.

This results in slightly less code, but code that is much more readable.
It has the advantage of putting everything together in one place, all of
the code is self documenting, help messages are auto-generated, choices
are automatically enforced, and the syntax is much less C like, taking
advantage of python features and idioms.

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>
Acked-by: Matt Turner <mattst88@gmail.com>