cfg standalone: add options to filter out a set of functions.

makes it easier to see the stuff we care about.  this
unfortunately doesn't filkter out edges *to* to the functions, we
might think about doing that someday.
cfg: make the shell script use the new filtering option
test programs: make sure functions don't get inlined.

doesn't seem to matter for the analysis, but makes it a pain to
visually inspect and determine if something is relevant.
add a bunch of new test programs.
cfg: add .gitignore for simple CFG printing object files.