Micro cleanup: use an array of const char, rather than an array of char, as the
type of the string literal implicitly used for a raw user-defined literal call.
No test; this has no semantic impact.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173309 91177308-0d34-0410-b5e6-96231b3b80d8