Emulate more functions

[mr-tz]

Currently FLOSS only emulates the top 10 or so decoding function candidates.

Improvement ideas on this:

• increase function count
• emulate all user functions (needs library ID, likely slow, so maybe need timeout)
• adding other heuristics to e.g.
  • backtrace from relevant APIs, see #279
  • always emulate the first N functions (sorted by FVA)

[williballenthin]

might also try emulation a couple times for each candidate, and if they yield results, keep going, otherwise move along.