SemaChecking.cpp

This reverts commit r283802. It introduces temporarily static
initializers, because StringRef ctor isn't (yet) constexpr for
string literals.
I plan to get there this week, but apparently GCC is so terrible
with these static initializer right now (10 min+ extra codegen
time was reported) that I'll hold on to this patch till the
constexpr one is ready, and land these at the same time.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@283920 91177308-0d34-0410-b5e6-96231b3b80d8