Unify the decision of how to emit property getters and setters into a

Unify the decision of how to emit property getters and setters into a
single code path.  Use atomic loads and stores where necessary.  Load and
store anything of the appropriate size and alignment with primitive
operations instead of going through the call.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@139580 91177308-0d34-0410-b5e6-96231b3b80d8