forked from amazingfate/loongoffice
...with glGenerateMipmap (since OpenGL 3.0) or GL_GENERATE_MIPMAP (since OpenGL 1.4). Appears to make slide transitions not worse on Linux and Mac OS X, while actually improving them on Windows (where the transitions were rendered in just white w/o textures), at least on the specific machines I tested on. Change-Id: I1e4c115223521acd3f254bdbf0330a7830160a9c