[GLES2] Fix usage of PF_SHORT_RGB and RGBA pixel formats.
[GLES2] Fix usage of PF_SHORT_RGB and RGBA pixel formats.

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branch : v1-9

jhu-lcsr-forks/ogre,jhu-lcsr-forks/ogre,jhu-lcsr-forks/ogre,jhu-lcsr-forks/ogre,jhu-lcsr-forks/ogre