Makefile.vc: add a 'legacy' RTLIBCFG option

disables buffer security checks (/GS-) and any machine optimizations
(e.g., sse2)

fixes issue #228

Change-Id: I81fa483dc1654199b2017626320383d2d63317dc
dec_neon: add RD4 intra predictor

based on the SSE2 version; a bit rough around the loads, but still ~38%
faster.

Change-Id: I22426d939a7354cbc9a85ca8c68235d6081b882f
Merge "Makefile.vc: add a 'legacy' RTLIBCFG option"
Merge "dec_neon: add RD4 intra predictor"