RenderManager#renderViewPort method leaves a clipRect in the OpenGL state

[richardTingle]

Within GLRenderer the renderViewPort method leaves a clipRect in the OpenGL state. This means that other calls to GLRenderer #copyFrameBuffer may give surprising (clipped) results

GLRenderer#renderViewPort should clear the clipRect state once it has finished its render

See https://hub.jmonkeyengine.org/t/blitted-to-frame-buffer-only-copies-part-of-source/47564 for an example of the problem caused

(I intend to put in a PR for this myself)