Avoid punning TypedValue* to String&/Array&/Object& in FCallBuiltin
(all three implementations). Our native function calling conventions
require passing pointers into a TypedValue for these types, and
pointers-to-scratch for return values.
In the HHIR case, I removed the optional "return pointer" argument
from the IR CallBuiltin instruction. The C++ value-passing ABI details
are now handled in cgCallBuiltin and are no longer exposed in the IR.
The argument types are still PtrTo*, but we handle the address fixups
in CodeGenerator.
smith
768a8bd238