adds NPOT option to TARGET_LINUX_ARM

* added an ifdef treating TARGET_LINUX_ARM similar to TARGET_OF_IPHONE, leaving the opportunity to

nvidia says anisotropic filtering with NPOT textures is no problem:
<http://developer.download.nvidia.com/assets/gamedev/docs/NVIDIA_OpenGL_2.0_Support.pdf> (page 6)

unfortunately i couldn't find equally good docs for ATI, but i should assume that they operate similarly, judging from the fact that the NVIDIA doc is from 2005, which, in computer/cat years was 49 years ago.

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>