Structurally, this is very similar to the existing Apple-DRI code, except I
have chosen to implement this using the __GLXDRIdisplay, etc. vtables (as
suggested originally in [1]), rather than a maze of ifdefs.  This also means
that LIBGL_ALWAYS_SOFTWARE and LIBGL_ALWAYS_INDIRECT work as expected.

[1] https://lists.freedesktop.org/archives/mesa-dev/2010-May/000756.html

This adds:

* the Windows-DRI extension protocol headers and the windowsdriproto.pc
file, for use in building the Windows-DRI extension for the X server

* a Windows-DRI extension helper client library

* a Windows-specific DRI implementation for GLX clients

The server is queried for Windows-DRI extension support on the screen before
using it (to detect the case where WGL is disabled or can't be activated).

The server is queried for fbconfigID to pixelformatindex mapping, which is
used to augment glx_config.

The server is queried for a native handle for the drawable (which is of a
different type for windows, pixmaps and pbuffers), which is used to augment
__GLXDRIdrawable.

Various GLX extensions are enabled depending on if the equivalent WGL
extension is available.

Otherwise the headers will be missing from the release tarball.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>

With reference to the libglvnd branch:

https://cgit.freedesktop.org/mesa/mesa/log/?h=libglvnd

This is a squashed commit containing all of Kyle's commits, all but two
of Emil's commits (to follow), and a small fixup from myself to mark the
rest of the glX* functions as _GLX_PUBLIC so they are not exported when
building for libglvnd. I (ajax) squashed them together both for ease of
review, and because most of the changes are un-useful intermediate
states representing the evolution of glvnd's internal API.

Co-author: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>

v2: - use const

v2: From Martin Peres
 - convert to the new drawable interface
 - delete dead code after the dropping of some vfuncs
 - delete the width and height attributes since they are found in the helper

Signed-off-by: Boyan Ding <boyan.j.ding@gmail.com>
Signed-off-by: Martin Peres <martin.peres@linux.intel.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>
Reviewed-by: Emil Velikov <emil.velikov@collabora.co.uk>

v2: From Martin Peres
 - Try to fit in the 80-col limit as much as possible

v3: From Martin Peres
 - introduce loader_dri3_helper.la to avoid dragging the xcb dep everywhere (Kristian & Emil)
 - get rid of the width, height, dri_screen and is_different_gpu vfuncs (Kristian)
 - replace the create/destroy functions with init/fini for dri3 drawables
 - prefix static functions with dri3_ and exported ones with loader_dri3 (Emil)
 - keep the function definition consistent (Emil)

Signed-off-by: Boyan Ding <boyan.j.ding@gmail.com>
Signed-off-by: Martin Peres <martin.peres@linux.intel.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>
Reviewed-by: Emil Velikov <emil.velikov@collabora.co.uk>

Add a macro GL_LIB_NAME to hold the filename that configure comes up with
based on the --with-gl-lib-name and --enable-mangling options.

In driOpenDriver, use the GL_LIB_NAME macro instead of hard-coding
"libGL.so.1".

v2: Add an #ifndef/#define for GL_LIB_NAME so that non-autoconf builds will
    work.
v3: Fix the library filename in the Makefile.

Signed-off-by: Kyle Brenneman <kbrenneman@nvidia.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Cc: "10.6 11.0" <mesa-stable@lists.freedesktop.org>

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>