Update EGL and GLES headers.

Notable new extensions:
EGL_EXT_image_gl_colorspace
GL_EXT_EGL_image_storage
GL_EXT_clip_control
GL_KHR_parallel_shader_compile

The first two extensions will be required in P for devices with the feature
android.vr.high_performance.

Changes compared to Khronos versions of the headers:

1. The Khronos headers contain a recent fix to remove the incorrectly
   named function glMultiDrawElementsBaseVertexOES, which should have
   the EXT prefix according to the extension specification. However,
   frameworks/base references that function in libs/hwui/debug, so it
   was teomprarily added back to the gl2ext.h and the .in files.
   See ag/3831170 and this link for further information:
   https://github.com/KhronosGroup/OpenGL-Registry/issues/81

2. eglext.h was modified to add the undocumented and deprecated
   EGL_ANDROID_image_crop extension. See bug 15287899 for context.

This also tweaks the glgen script to ignore Windows-specific items.

Bug: 74131503
Bug: 76152545
Test: Built and ran a few OpenGL-related CTS tests on Pixel XL.

Change-Id: I5b365c114b09228a6ead291c08e5330153f75748