IMCC

• enable GC while parsing
  • allows more extensive use of PMCs, which encourages more sharing with the rest of the Parrot ecosystem (eg: PackFile PMCs, PIRATE)
• constant unfolding
  • unimplemented const-variants of ops should get unfolded to multiple 'set' ops followed by the non-const variant of the op
  • reduces demand for umpteen op variants (op-bloat)
• consider salvaging optimizer components, possibly for a pbc_to_pbc transformation tool or an in-memory inplace optimizer
• work on isolating IMCC into separately loadable module
• work on simple low-level replacement (PASM2)

Bytecode

• make subs first class entities. this would match the rest of Parrot more closely and solve a lot of issues.
• make same-pbc backreferences work.
  • would reduce the total size cost of deeply-inner'd subs in PBCs
  • would make autoclose work from pbc.
  • would makethis also does the hard parts for cross-pbc references (requested by 6model)
• document format