Resize: make internal resizer GetFrame() re-entrant.
Merge branch 'MT' of upstream into mt-filter-fix
Resize: remove Env pointer from class storage + pre-cast env pointer to env2 before using.
Resizer: add MT mode api call.
Register Turn filters as re-entrant. Also some casing fixes.
Register transform filters as re-entrant. Some slight refactoring.
Fix VerticalReduceBy2 not working on Y8
Register ReduceBy2 functions as re-entrant.
Register planeswap functions as re-entrant.
Register Merge and Limiter filters as re-entrant.
Register all layer functions as re-entrant.
Reduce instruction set requirements to plain old SSE.
Check in CMake if selected VC++ version is supported.
Resizer: fix MT mode registration
Resizer: use Env->Allocate in ResamplingProgram.
Overlay: make it NICE_PLUGIN
Update histogram filter for MT. Small refactorings.
Make focus and grayscale filters re-entrant.
Cleanups
Fix duplicate zero thread id.