This diff eliminates setOpEqual() and appendOpEqual() from Variant, and
it also removes several methods from ObjectData: o_assign_op(), o_argval(),
setDummy(), init(), cloneDynamic(), o_setPublicWithRef(), o_i_set(),
getRedeclaredParent(), and o_propForIteration().
This diff also makes several methods in ObjectData non-virtual: destruct(),
o_toIterArray(), and o_getDynamicProperties(). To achieve this, some of the
logic from Instance was moved to ObjectData.
Finally, this diff gets rid of "hhvm/externals_stubs.cpp" and
"runtime/eval/eval.cpp".
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.
andrewparoski