C++: Consider '^//[/!][^\n]*' as doxygen comment

Now everything following '///' or '//!' is a doxygen comment.

This simplification fixes also the bug ('\n' was considered as part of
the doxygen comment and led to strange highlighting).

Task-number: QTCREATORBUG-8921

Change-Id: I6dae3b80ec11400f2f623897257782a80860a7f3
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>

src/libs/3rdparty/cplusplus/Lexer.cpp

@@ -368,11 +368,7 @@ void Lexer::scan_helper(Token *tok)
 
             if (_yychar == '/' || _yychar == '!') {
                 yyinp();
-
-                if (_yychar == '<' || _yychar != '/') {
-                    yyinp();
-                    doxy = true;
-                }
+                doxy = true;
             }
 
             while (_yychar && _yychar != '\n')