Create a emitCXXStructor function and make the existing emitCXXConstructor and
emitCXXDestructor static helpers.

A next patch will make it a helper in CGCXXABI.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@217804 91177308-0d34-0410-b5e6-96231b3b80d8