Support GETIV
original commit by miura1729
https://github.com/miura1729/mruby/commit/8c4c4ee518bd937f8103f5f560f613accc83679c
OP_LOADL writes 4bytes
bugfix for OP_GETIV
Support SETIV
original commit by miura1729
https://github.com/miura1729/mruby/commit/6848ed04fec667b67350f58961bfe5357e2d5731
Support GETUPVAR/SETUPVAR
original commit by miura1729
https://github.com/miura1729/mruby/commit/9a8248669929aa068c73d4101759b8b5e67840c7
Support OP_ADD, OP_SUB
original commit by miura1729
https://github.com/miura1729/mruby/commit/926f867a67a960b2008a67a0378df853c926751c
Support GETCONST
original commit by miura1729
https://github.com/miura1729/mruby/commit/857a0a6f401585a86671e595c1fd7f9f34915f0b