Add basic implementation of Lookup.find{Virtual,Static,Constructor}.

- Implemented using existing reflection APIs.
- Access checking is performed in Java and not by the runtime.

bug: 30550796
Test: make checkbuild
Test: art/tools/run-libcore-tests.sh --mode=host --variant=X64
Change-Id: I3f65d96851272592c7ba0898ea9e34889adca48b