c++ IRGen. In trivial cases that object is going into static
storage and thus is implicitly zero-initialized, no need to
do C++11 memory model. This patch unconditionally detects
such condition and zeroinitializer's the variable.
Patch has been commented on and OKed by Doug off-line.
// rdar://12897704


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172144 91177308-0d34-0410-b5e6-96231b3b80d8