Improve skipping (#368)
Improve skipping (#368)

* foo

* the pass has some logic for skipping optimizations, with various use
cases such as binary search for debugging. this patch makes souper
skip more work when operating in this mode, should otherwise make no
functional changes

regehr/souper,jubitaneja/souper,google/souper,rsas/souper,google/souper,rsas/souper,google/souper,jubitaneja/souper,rsas/souper,regehr/souper,jubitaneja/souper,regehr/souper,rsas/souper,jubitaneja/souper,regehr/souper,jubitaneja/souper,regehr/souper,google/souper,jubitaneja/souper,rsas/souper,rsas/souper,google/souper