Tighten up the set of operator new/operator delete calls we're permitted to

Tighten up the set of operator new/operator delete calls we're permitted to
optimize, to follow the permissions granted in N3664. Under those rules, only
calls generated by new-expressions and delete-expressions are permitted to be
optimized, and direct calls to ::operator new and ::operator delete must be
treated as normal calls.

llvm-svn: 186799