Add MRB_RUBIC_BOXING mode
Add MRB_RUBIC_BOXING option to nios2-rubic
Basic support from OP_NOP to OP_ASET
Nios2 native code generation support
Declaration of mrb_vm_state
Rename MRB_RUBIC_BOXING to MRB_32BIT_BOXING
Move machine header to src/
Replace all mkop_xxx to make_OP_xxx
Refactoring of boxing treatments in value.h
Debug code for arena check
Revert "Debug code for arena check"

This reverts commit 82d734100184ad0afa991d3fedf0e4787540f9e5.
Fix make_OP_METHOD
Temporarily disable nios2