C++ Mode - Fontify "class Foo {\n ~Foo() noexcept;" correctly

This fixes bug #49787.

* lisp/progmodes/cc-engine.el (c-forward-decl-or-cast-1): (In `if' form just
before CASE 8) Remove the (not ...) around the (looking-at
c-after-suffixed-type-maybe-decl-key).

* lisp/progmodes/cc-fonts.el (c-font-lock-complex-decl-prepare): Add
`c-not-decl' to the values of c-type which are erased at the start of a
fontification.

lisp/progmodes/cc-engine.el

@@ -10571,8 +10571,8 @@ This function might do hidden buffer changes."
 			backup-maybe-typeless
 			(when c-recognize-typeless-decls
 			  (or (not got-suffix)
-			      (not (looking-at
-				    c-after-suffixed-type-maybe-decl-key))))))
+			      (looking-at
+			       c-after-suffixed-type-maybe-decl-key)))))
 	       ;; Got an empty paren pair and a preceding type that probably
 	       ;; really is the identifier.  Shift the type backwards to make
 	       ;; the last one the identifier.  This is analogous to the

lisp/progmodes/cc-fonts.el

@@ -940,7 +940,8 @@ casts and declarations are fontified.  Used on level 2 and higher."
 			'(c-decl-arg-start
 			  c-decl-end
 			  c-decl-id-start
-			  c-decl-type-start)))
+			  c-decl-type-start
+			  c-not-decl)))
 	     (1- (point))
 	   pos)
 	 limit 'c-type)))