DR1213: element access on an array xvalue or prvalue produces an xvalue. In the

DR1213: element access on an array xvalue or prvalue produces an xvalue. In the
latter case, a temporary array object is materialized, and can be
lifetime-extended by binding a reference to the member access. Likewise, in an
array-to-pointer decay, an rvalue array is materialized before being converted
into a pointer.

This caused IR generation to stop treating file-scope array compound literals
as having static storage duration in some cases in C++; that has been rectified
by modeling such a compound literal as an lvalue. This also improves clang's
compatibility with GCC for those cases.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@288654 91177308-0d34-0410-b5e6-96231b3b80d8