making call stable a posteriori

INVOKEVIRTUAL and INVOKEINTERFACE are unstable at call site,
however, if the declaration site is stable, we treat call sites as stable
integration test data change
fix: cycle (identity) dominates conditional NPE
delta in data after fix
tuning null -> ... analysis

Handling NPE in null -> ... analysis. If at a given branch NPE is detected (via direct dereferencing), then the result of this branch is NPE.
delta in integration test data after tuning of null -> ... analysis
Merge pull request #17 from ilya-klyuchnikov/stable-calls

Stable calls