remove calls from loopheads: make tail-recursive
calls
MFS: remove unaccessed entry
MFS: remove singledef from initial locset
Merge branch 'master' of github.com:skcho/zooberry
When call is loophead, we change widening point to its successor, assuming that the successors do not include any cother calls. In this setting, we have to disable b_widen in fixpoint algorithm
add sanity check: calls are not loopheads