call LLViewerTexture::isMemoryForTextureLow() less often and only for ATI cards.
call LLViewerTexture::isMemoryForTextureLow() less often and only for ATI cards.

gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm