hg: openjfx/11-dev/rt: 8219008: Update OpenGL Headers to version 4.6

[johan at lodgon.com]

Changeset: c3a20dcea540
Author:    kcr
Date:      2019-02-19 13:22 -0800
URL:       https://hg.openjdk.java.net/openjfx/11-dev/rt/rev/c3a20dcea540

8219008: Update OpenGL Headers to version 4.6
Reviewed-by: jvos, arapte

+ modules/javafx.graphics/src/main/legal/opengl_fx.md
! modules/javafx.graphics/src/main/native-prism-es2/GL/glext.h
! modules/javafx.graphics/src/main/native-prism-es2/GL/glx.h
! modules/javafx.graphics/src/main/native-prism-es2/GL/glxext.h
! modules/javafx.graphics/src/main/native-prism-es2/GL/wglext.h
+ modules/javafx.graphics/src/main/native-prism-es2/KHR/khrplatform.h