Let hhbbc know that invariant_violation always fails

Summary: hhbbc does not know about call_user_func_array(), so when

  invariant(condition(), ...);

is rewritten as

  if (!condition()) {
    invariant(false, ...);
  }

it has trouble figuring out that invariant(false, ...) never
falls through.

After this diff, hhbbc figures out correctly that invariant(false, ...)
returns TBottom, but still cannot fully use this knowledge.

Reviewed By: @ptarjan, @elgenie

Differential Revision: D1595071
Kill HHIREnableCalleeSaveOpt runtime option

Summary: It isn't used anymore.

Reviewed By: @swtaarrs

Differential Revision: D1593488