testbench: port x264 stack & register check code
pixelharness: stack-check all asm pixel primitives
update x86inc.asm
primitives: nit
improve by LEA to ADD in cvt32to16_shr
cmake: export YASM_FLAGS from CMakeASM_YASMInformation.cmake

This avoids duplicate logic in other cmake scripts

--HG--
extra : amend_source : 68cd2ecf479341d1eef9dfe5fe6609b6795488c1
move checkasm-a.asm to the test/ folder (fixes linux link)

--HG--
rename : source/common/x86/checkasm-a.asm => source/test/checkasm-a.asm
align the stack for GCC x86_32 builds

For all threads x265 creates, align the stack immediately in the call to
threadMain().

The API calls do not appear to require an aligned stack; all primitives that
require stack aligned buffers are called from frame encoder or worker pool
threads

--HG--
extra : amend_source : 9bab840de1dfd5234c63149bf7a082d8292a278e
fixups for testbench build on Windows
TComMotionInfo: nit