v1.4.2, back to speed, add llvm

Changelog

• (20241210) v1.4.2
  • Rewrite all external assembly codes (fdct, idct, h263 and mpeg quant-dequants) to Intel intrinsics.
    It's now quicker - sometimes significantly - than the original.
  • Source: changed Windows specific threading code into C 17 version.
  • Source cleanup: removed lots of never used test codes from the source, rewrite some others. Move to cpp.
  • Add ability to pass Avisynth+ frame properties
  • Add support for any 8 bit planar YUV(A) or Y format (was: YV12 only)
  • Copy A alpha plane as well, if exists. (The filter works only on luma channel, other planes are simply copied)
  • Fix: add meaningful error message (Issue #2) for clips with non-mod8 width or height dimensions (was: out of memory)
  • Add Clang-cl LLVM build option, make source Clang friendly
  • Speedup examples:

qtype	32 bit clangcl	32 bit msvc	32 bit old 1.3	64 bit clangcl
1	6.12 fps	5.49 fps	5.40 fps	6.56 fps
2	6.67 fps	5.93 fps	5.28 fps	7.08 fps
3	4.09 fps	3.61 fps	3.22 fps	4.29 fps
4	6.66 fps	5.98 fps	5.29 fps	7.16 fps