Revert "Use official headers to define GL_ARB_texture_rectangle."

Revert "Use official headers to define GL_ARB_texture_rectangle."

This reverts commit 9869bedb56822d19c9bfbdb33f6af061da8e6106.

It broke 32-bit builds on Windows because GLsizeiptr and GLintptr are
defined as different types (int vs. long) in gl2.h and glcorearb.h.
See also https://github.com/KhronosGroup/OpenGL-Registry/issues/162

Change-Id: Ia7bd4accb1671529ce6da6849a1df76dceddcdee
Reviewed-on: https://swiftshader-review.googlesource.com/18068
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>