Make sure expression statements that generate ctrl flow are wellformed

Also, check all graphs after construction. I've seen enough bugs in
there to want this in.
Update mj-test submodule
Merge pull request #222 from TehMillhouse/ctrlflow_leakage

Make sure expression statements that generate ctrl flow are wellformed
Manually mature all blocks
Merge pull request #225 from Kha/very-mature

Manually mature all blocks as soon as possible
"I didn't say to merge just yet!"
Fix 'it' in mjis.opt tests
Add generic DataFlowAnalysis and reimplement constant folding on top of it