Implement invokesuper in optimizing.

- Ensure dex2oat is in PIC mode, as this will drive the decisions
  made in the compiler driver, and optimizing only suppots PIC
  anyway.

- Since invokesuper is sharpened into invoke-direct, also support
  sharpening of invokeinterface and invokevirtual.

Change-Id: I0a1bd79a13dc1c9e67e3cb11d38f0cd4459968ae