CC Mode: Move the handling of keyword auto into type handling for C++.

CC Mode: Move the handling of keyword auto into type handling for C++.

This should allow auto, const, static, ... to be in any order.

* lisp/progmodes/cc-engine.el (c-forward-type): New return value 'no-id for
when auto precludes the parsing of a type identifier.  Adapt processing for
this.
(c-forward-decl-or-cast-1): Use the new facility from c-forward-type.

* lisp/progmodes/cc-langs.el (c-type-modifier-prefix-kwds): Insert the value
of c-no-type-kwds into the value.
(c-no-type-kwds, c-no-type-key): New lang consts/vars, basically "auto".
(c-typeless-decl-kwds, c-modifier-kwds): Remove "auto" from the C++ value.