CodeGen support for function-local static thread_local variables with

CodeGen support for function-local static thread_local variables with
non-constant constructors or non-trivial destructors. Plus bugfixes for
thread_local references bound to temporaries (the temporaries themselves are
lifetime-extended to become thread_local), and the corresponding case for
std::initializer_list.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179496 91177308-0d34-0410-b5e6-96231b3b80d8