Add a reverse hash table to fully simulate previous gc code

  The code in reset_invalidated_inline_caches has been reinstantiated,
as it was likely a cause of problems. Now there is also a reverse
hash table, to map a jit code pointer into a method_entry, so that
it can fully simulate the lightning 1 logic.

  This change actually makes it fail test 46, but pass 47, 49, 50,
fail 51... so it reversed some Ansi tests failures, but pass way
more tests now.