mapi/new: import mapi scripts from glvnd

mapi/new: import mapi scripts from glvnd

Currently we have over 20 scripts that generate the libGL* dispatch and
various other functionality. More importantly we're using local XML
files instead of the Khronos provides one(s). Resulting in an
increasing complexity of writing, maintaining and bugfixing.

One fairly annoying bug is handling of statically exported symbols.
Today, if we enable a GL extension for GLES1/2, we add a special tag to
the xml. Thus the ES dispatch gets generated, but also since we have no
separate notion of GL/ES1/ES2 static functions it also gets exported
statically.

This commit adds step one towards clearing and simplifying our setup.
It imports the mapi generator from GLVND.

  012fe39 ("Remove a couple of duplicate typedefs.")

v2: use local genCommon.py

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>