[PATCH] [OpenCL] Add string literals to the constant address space.

[Jordan Rose]

  Does LangOpts.OpenCL imply LangOpts.ConstStrings? It probably should, just in case anything else is checking to see if it can rely on all string constants being const. You could even then (in a followup patch) complain if anyone tried to turn this off, e.g. with -fwritable-strings.

  (I see that you still have to special case the address space.)

http://llvm-reviews.chandlerc.com/D894