cmake: cleanup compiler determination
cmake: make intel C++ compiler detection independent of env vars
cmake: repair ICL nmake builds - do not use yasm custom rule with nmake
cmake: default value for X265_VERSION
pixel: allow clang to build AVX2 pixel primitives functions
pixel: remove unreferenced sse_pp4 function
pixel: remove unreferenced cvt16to32_t and cvt32to16_t primitives
piclist: ensure a TComPic is not enqueued in two lists at once