Check access to friend declarations. There's a number of different

things going on here that were problematic:
  - We were missing the actual access check, or rather, it was suppressed
    on account of being a redeclaration lookup.
  - The access check would naturally happen during delay, which isn't
    appropriate in this case.
  - We weren't actually emitting dependent diagnostics associated with
    class templates, which was unfortunate.
  - Access was being propagated incorrectly for friend method declarations
    that couldn't be matched at parse-time.

llvm-svn: 161652