Merge REBTYS to REBWRS

To void substle breakage caused by the misalignment of the two structures.
For consistency
Revert "[Makefile] Let user override compiler"

This reverts commit f8bed26ea098dfa0b7f53e2c531cda3f40fc66fb.

This makes cross-compile for windows fail, CC will evaluate to "cc", it
seems that the CC is already predefined in make
Fix builds for windows
Check END! only for real blocks

Call_Block abuses block for storing the pointers
[Makefile] fix libffi path for 32-bit linux systems

Tested on Arch linux
Fix qsort for 32-bit systems
[Makefile] Fix libffi path for mingw builds