a patch from Yannick Scherer
No forking on enter; why did we think this is necessary?
Reduce thread creation weirdness.
reimplemented the fwtn solver
made "dead-code"==bottom for eq-solver
Simple thread uniqueness.
Post-processing for thread uniquness, using desperate hacks.
fixed loop head recognition (hopefully)
sorry
localized widening (using pre-dominators)
pre-dominator set pruning
Merge remote-tracking branch 'upstream/master'

Conflicts:
	src/util/defaults.ml