BytecodeInstructions#capture should record metadata array as individual literals,
so that the resulting bytecode is composed only of marshallable primitives.

--HG--
extra : amend_source : 73278e62ff8cc4950f67cf0b09ac093334835d0e
Add skip decorator to BasicSpec
Skip MycoGrammar related tests for now (too slow)
Use only marshallable primitives for captors
Add BytecodeParser#(save|load)_prototype