[GLES] speed up blending

(texture * color) costs us an extra operation on Mali when sent as varying.
Instead, since textures use the same color for the entire render, send it as
a uniform instead.

This does not apply to fonts, since the font and its shadow are rendered
together, and may not share a color (tested and looks bad).

This increases fps anywhere heavy blending is done.
[GLSL] cut diffuse+blend render time by 1/3

Mainly seen when we're fading in/out.

Mali likes this ordering better for some reason, ops go from 3 to 2 (according
to their profiler). Verified with PVR's compiler that there is no change, it's
2 there either way.
[GLES] Batch textures and their borders

Gives a considerable speedup in scenes with many bordered images
(like settings).
skip dxt compression on all arm boards

The only chipset I'm aware of that can do dxt on arm is Tegra, and that's not
worth slowing everyone else down
[GLES] clear screen (in the right place) before shutdown
fixed, hook GetPreferredResolution in WinSystemEGL