Parse C++ inher-intro when there's a template split over 2 lines.

Parse C++ inher-intro when there's a template split over 2 lines.

* progmodes/cc-engine.el (c-guess-basic-syntax CASE 5C): Code more
rigorously the search for "class" etc. followed by ":".

* progmodes/cc-langs.el (c-opt-<>-sexp-key): Make the value for
random languages a regexp which never matches rather than nil.