ForceDom and ScopeResolution are really slow

[skrynski]

The abstract interpretation steps are to blame for 99.99% of the time spent on these analyses.
Also, revisit DeadStoreRemoval.

As an easy example, please look into /rir/tests/matrix_regression.r . It takes about 2 minutes to run, which breaks down into:

• PIR optimization 1 min . ScopeRes takes 20s .
  The following two lines alone take up 8s of the execution time

ScopeAnalysis analysis(cls, code, log);
analysis();

• LLVM translation compilation 1 min

File runs in less than a second on vanilla R.