CppHighlighter: highlight all functions/methods.

- Highlight all function/methods (not just virtual methods).
- Highlight as a function even if number of arguments does not match. In
  that case, add a diagnostic message to indicate there are too many/too
  few arguments.
- Fix highlighting of parameters in function declarations.
  These used to be handled indiferently, and they could be mistaken for
  type or field references.
- Properly highlight template method calls.

Change-Id: I6ab463996dda47554839f482da47f561f76663a7
Reviewed-by: Erik Verbruggen <erik.verbruggen@nokia.com>

src/plugins/texteditor/texteditorconstants.h

@@ -129,6 +129,7 @@ const char C_TYPE[]                = "Type";
 const char C_LOCAL[]               = "Local";
 const char C_FIELD[]               = "Field";
 const char C_STATIC[]              = "Static";
+const char C_FUNCTION[]            = "Function";
 const char C_VIRTUAL_METHOD[]      = "VirtualMethod";
 const char C_KEYWORD[]             = "Keyword";
 const char C_OPERATOR[]            = "Operator";