FFI: Compile conversions from functions to function pointers.
Check for failure to mark memory as executable (restricted kernels).
Merge branch 'master' into v2.1
Fix handling of redundant PHIs.
Merge branch 'master' into v2.1
Fix GC steps threshold handling when called by JIT-compiled code.

Thanks to Cheng, Long.
Merge branch 'master' into v2.1
Fix for last commit
Merge branch 'master' into v2.1
Fix type punning alias analysis for constified pointers.
Merge branch 'master' into v2.1
FFI: Clarify ffi.cdef behavior.
Merge branch 'master' into v2.1
Improve msvcbuild.bat static linking.
Merge branch 'master' into v2.1
Follow-up fix for GC step threshold fix.
Merge branch 'master' into v2.1
Respect jit.off(func) when returning to a function, too.
Merge branch 'master' into v2.1
Abstract out post-registration handling of pre-registered modules.