It was only used to fold SimpleFunctionCall nodes. Ive setup enough
of the runtime that we can call invoke (which goes through hhvm's
normal Func dispatch), and then removed it.
This basically targetted symbols.php, and Globals, but ended up
killing a lot more. I could keep adding more and more, but
this seems like a good point to stop and continue with
another diff.
This change is mostly for FB internal organizational reasons.
Building is not effected beyond the fact that the target now
lands in hphp/hhvm/hhvm rather than src/hhvm/hhvm.
mwilliams