[analyzer] operator new: Fix memory space for the returned region.

Make sure that with c++-allocator-inlining=true we have the return value of
conservatively evaluated operator new() in the correct memory space (heap).
This is a regression/omission that worked well in c++-allocator-inlining=false.

Heap regions are superior to regular symbolic regions because they have
stricter aliasing constraints: heap regions do not alias each other or global
variables.

Differential Revision: https://reviews.llvm.org/D41266
rdar://problem/12180598

llvm-svn: 322780