git: openjdk/jdk15u-dev: 8262392: Update Mesa 3-D Headers to version 21.0.3

[Andrew Brygin]

Changeset: a6ab0c8a
Author:    Andrew Brygin <bae at openjdk.org>
Date:      2021-09-20 14:06:53 +0000
URL:       https://git.openjdk.java.net/jdk15u-dev/commit/a6ab0c8ae65b23be754007f86f3369322a065276

8262392: Update Mesa 3-D Headers to version 21.0.3

Backport-of: 138d573c3567e9a51b1ac2b1de89b41c4b51ae93

! src/java.desktop/share/legal/mesa3d.md
! src/java.desktop/share/native/common/java2d/opengl/J2D_GL/gl.h
! src/java.desktop/share/native/common/java2d/opengl/J2D_GL/glext.h
! src/java.desktop/unix/native/common/java2d/opengl/J2D_GL/glx.h
! src/java.desktop/unix/native/common/java2d/opengl/J2D_GL/glxext.h
! src/java.desktop/windows/native/libawt/java2d/opengl/J2D_GL/wglext.h