Add option for saying which nginx binary to use

Summary: Some packages don't install it into $PATH

refs facebook/hhvm#3664

Reviewed By: @ptarjan

Differential Revision: D1544870
Use EqX instead of Eq for Obj/Num comparisons.

Summary: Converting an Obj to Int or Dbl will reenter the VM to raise a notice.

Reviewed By: @jano

Differential Revision: D1542454