FFI support.
FFI support.

vm_do_ffi:
  can't use type_sint for integers. (sizeof(int) != sizeof(intptr_t))
  'u' and 'c' codes.
vm_cget/vm_cset: support both buf and mem.
vm: sfromc opcode.

samrushing/irken-compiler,samrushing/irken-compiler,samrushing/irken-compiler,samrushing/irken-compiler