x86: Add CPU flag for the i686 cmov instruction

(cherry picked from commit 65345a5a30a0e866b6944c0e6184be3feca04335)
Signed-off-by: Diego Biurrun <diego@biurrun.de>

Conflicts:
	libavutil/cpu.c
	libavutil/cpu.h
x86: Only use optimizations with cmov if the CPU supports the instruction

Also fill in missing hash for AV_CPU_FLAG_CMOV addition in APIChanges.

(cherry picked from commit fe07c9c6b5a870b8f2ffcfac649228b4d76e9505)
Signed-off-by: Diego Biurrun <diego@biurrun.de>

Conflicts:
	libavcodec/x86/dsputil_mmx.c