XCore target: Lower ATOMIC_LOAD & ATOMIC_STORE

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201143 91177308-0d34-0410-b5e6-96231b3b80d8
XCore target: fix const section handling

Xcore target ABI requires const data that is externally visible
to be handled differently if it has C-language linkage rather than
C++ language linkage.

Clang now emits ".cp.rodata" section information.

All other externally visible constant data will be placed in the DP section.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201144 91177308-0d34-0410-b5e6-96231b3b80d8