10% faster table-less SSE2/NEON version of YUV->RGB conversion

* Precision is slightly different
* also implemented in SSE2 the missing WebPUpsamplers for MODE_ARGB, MODE_Argb, MODE_RGB565, etc.
* removing yuv_tables_sse2.h saved ~8k of binary size
* the mips32/mips_dsp_r2 code is disabled for now, since it has drifted away
* the NEON code is somewhat tricky

Change-Id: Icf205faa62cf46c2825d79f3af6725dc1ec7f052
11 files changed