Update bytecode.lua

on osx and according to "ANoFrillsIntroToLua51VMInstructions" it should be:
1 byte Size of int (in bytes) (default 4)
1 byte Size of size_t (in bytes) (default 4)
1 byte Size of Instruction (in bytes) (default 4)
1 byte Size of lua_Number (in bytes) (default 8)
so Instruction after size_t...
Merge pull request #1 from ubaldus/patch-1

Correction to bytecode.lua (original version would fail if instruction length differs from size_t)