Add hints for the (future) optimizer in method info.

The hints are:
* whether the method is an accessor (getter or setter)
* whether it has the @inline annotation

These information are currently unused, but the (future) inlining
optimizer might use them as heuristics. Since this is a binary
incompatible change, it had better be added now.
Merge pull request #534 from sjrd/optimizer-hints

Add hints for the (future) optimizer in method info.