add a -souper-no-infer command line option that is useful for quickly...

loading LHSs into the cache

add a tool cache_infer that runs infer() on each LHS in the cache; this is
useful for doing synthesis work without dealing with the tedium of building
software; it automatically uses all CPUs

add a couple of "parse only" options to souper-check so that cache_dump can
ensure that cache LHSs parse without incurrent the cost of running the solver

remove the spinner from cache_dump

a bit of refactoring in cache_dump