It seems better if the caller allocates the memory for the RGBA buffer.

For example it allows to use std::vector<> and call the method

Change-Id: Id4b8e33838d358dd242d0176e42558505fa8d4a3
Mirror vertically the texture bitmaps for OpenGL

In case of glTF models it saves a Mirror() call.
In case of OpenGL charts it avoid flipped texts.

Change-Id: I1ac980e16bcb5ba6a9a025b638aaac3b08b4aab3