Reduce instruction set requirements to plain old SSE.
Check in CMake if selected VC++ version is supported.
Cleanups
Fix duplicate zero thread id.
Fix MTGuard::EnableMT() working with invalidated script function parameters (fixes mode 2).
Add MT mode getters to some internal filters.
Refactor MTGuard's factory function.
Add new guard to BufferPool to detect metadata corruptions from both directions.
Add AvsAllocType enum.
Merge branch 'MT' of upstream into mt-filter-fix, resolving conflicts.
Resizer: Fix mismatched alloc/free