Fixes for Generic JNI

This fixes some linking issues and native code retrieval errors.
All host tests are functional with this change.

Make ArtMethod::GetFrameSizeInBytes() templated to bypass the
embedded sanity check. Necessary for fix-up decision.

Add ArtMethod metadata fix-up code to ClassLinker::LinkCode.
Necessitates new parameters to access the shorty and compute
the frame size.

Fix handling the JNI dlsym lookup stub in the generic JNI code.

Change-Id: I4173b0fbb1ba5b1bcbee1bb340cfdd08a54767e5