Fix fatal JVM crash on macOS during hardware instancing (LwjglGLExt ARB extensions)

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On macOS, OpenGL Core Profile drivers strip legacy ARB extension function pointers even when equivalent functionality is available via core entry points. LwjglGLExt was unconditionally dispatching through ARB (e.g. ARBDrawInstanced.glDrawArraysInstancedARB), causing an immediate fatal native crash on any instanced draw call.

Changes

• jme3-lwjgl3/LwjglGLExt.java: Each method now queries GL.getCapabilities() at runtime and dispatches to the core GL entry point when available, falling back to the ARB extension only for older contexts (e.g. GL 2.0 + ARB extensions) that predate the core promotion.

Method	Core (preferred)	Fallback
glDrawArraysInstancedARB	GL31.glDrawArraysInstanced	ARBDrawInstanced
glDrawElementsInstancedARB	GL31.glDrawElementsInstanced	ARBDrawInstanced
glVertexAttribDivisorARB	GL33.glVertexAttribDivisor	ARBInstancedArrays
glGetMultisample / glTexImage2DMultisample	GL32.*	ARBTextureMultisample
UBO methods	GL30/GL31.*	ARBUniformBufferObject
Sync methods	GL32.*	ARBSync
SSBO / program resource	GL43.*	ARBShaderStorageBufferObject / ARBProgramInterfaceQuery

Example dispatch pattern applied throughout:

@Override
public void glDrawArraysInstancedARB(int mode, int first, int count, int primCount) {
    if (GL.getCapabilities().OpenGL31) {
        GL31.glDrawArraysInstanced(mode, first, count, primCount);
    } else {
        ARBDrawInstanced.glDrawArraysInstancedARB(mode, first, count, primCount);
    }
}

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Pull request overview

This PR updates the LWJGL3 GLExt implementation to avoid native JVM crashes on macOS Core Profile by preferring core OpenGL entry points (when available) instead of dispatching through legacy ARB extension function pointers that may be stripped by the driver.

Changes:

• Switch instancing calls (glDraw*Instanced*, glVertexAttribDivisor*) to dispatch to core GL methods when the corresponding core version is available, otherwise fall back to ARB extensions.
• Apply the same core-preferred dispatch pattern to multisample texture functions, UBO-related functions, sync objects, and several newer-program-interface/SSBO-related functions.
• Improve class-level Javadoc (including a typo fix and explanation of the macOS Core Profile issue).

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