dfttest v1.9.4.4

Changes:

2020.03.23 v1.9.4.4 - pinterf

• fix: make fft3w plans thread safe
• MSVC project to VS2019, add v142, v141_xp and ClangCl config.
• refresh avisynth headers
• source to C++17 strict conformance
• AVX option is always available

2018.10.14 v1.9.4.3 - DJATOM

• Fixed one nasty bug, causing crash on non-AVX CPUs.

2017.09.04 - DJATOM

• Adaptive MT mode: MT_MULTI_INSTANCE for threads=1 and MT_SERIALIZED for > 1 internal
• Compilation: silence #693 for Intel Compiler

2017.08.14 - DJATOM

• x64 ready: ported almost all inline asm to intrinsics (dropped some SSE functions, we're in 2017 now).
• AddMean and RemoveMean got their AVX codepaths.
• PlanarFrame updated from JPSDR's NNEDI3 repo (x64 friendly, HBD ready).
• proc0_16 got SSE2 codepath (I can see noticeable speed-up against old version).
• opt parameter change: 2 - SSE/SSE2, 3 - SSE/SSE2/AVX codepath is used.