Revert an incorrect assumption in the initial commit

  Now it does "exactly" what the initial code did to map a nativeCode
pointer to a method_entry, just that now it does lookup the reverse
hash table, as the nativeCode is no longer appended to a variably
sized method_entry structure.

  Now, on i586 it has the exact same behavior, regarding to test
cases as the original "lightning 1" build. Pass all test cases, until
117: DebugTools, where it hangs.