[windows] update SDL-2.0.0 to 2.0.1. Fixes issue 6793.
VideoCommon: create native texture pool

We often need the same native texture objects for new textures. This commit
try to avoid destroying and creation of this textures by pooling them.

This should be a big performance gain for some efb2ram games as they may
overwrites partially a cached texture (which would be deleted) and afterwards
try to read it.

Creating/destroying sounds like an easy task, but it isn't. eg the nvidia ogl
driver synchonize their threads do avoid use-after-free issues.
[ARM] Fix an issue with the data offset in LoadStore operations. Thanks to PPSSPP.
[ARM] Minor idle skip optimization in bx.
ogl: check default framebuffer for msaa

default framebuffer must not be sampled, so throw a panicalert if it is