Handle C++11's "auto" and "decltype" constructions.

Handle C++11's "auto" and "decltype" constructions.
cc-engine.el (c-forward-type): Enhance to recognise and return 'decltype.
(c-forward-decl-or-cast-1): New let variables backup-kwd-sym,
prev-kwd-sym, new-style-auto.  Enhance to handle the new "auto" keyword.

cc-fonts.el (c-font-lock-declarations): Handle the "decltype" keyword.
(c-font-lock-c++-new): Handle "decltype" constructions.

cc-langs.el (c-auto-ops, c-auto-ops-re): New c-lang-defconsts/defvars.
(c-haskell-op, c-haskell-op-re): New c-lang-defconsts/defvars.
(c-typeof-kwds, c-typeof-key): New c-lang-defconsts/defvars.
(c-typeless-decl-kwds): Append "auto" onto the C++ value.
(c-not-decl-init-keywords): Also exclude c-typeof-kwds from value.