[analyzer] Inline C++ operator new when c++-inline-allocators is turned on.

This will let us stage in the modeling of operator new. The -analyzer-config
opton 'c++-inline-allocators' is currently off by default.

Patch by Karthik Bhat!

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@201122 91177308-0d34-0410-b5e6-96231b3b80d8