[Mesa-stable] GL/GLES header nominations for 18.2

[Emil Velikov]

Hi all,

As pointed out in [1] one cannot include both GL and GLES headers at
the same time.
Which leads to problems building gst, qt5 and according to the webs webkit.

Issue is resolved on the 18.3 branch and in master with the following commits:

f7d42ee7d31 include: update GL & GLES headers (v2)
87c156183cd configure: install KHR/khrplatform.h when needed
e02f061b690 meson: install KHR/khrplatform.h when needed

Note: the first commit is quire bulky, so one may consider picking
only the hunk with the typedefs.

HTH
Emil

[1] https://bugs.freedesktop.org/show_bug.cgi?id=105328