use -Wunused-parameter with gcc for consistency with MSVC and other compilers which warn about this; fix the uncovered warnings in wxGTK

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@49376 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/textentry.cpp

@@ -42,9 +42,9 @@ extern "C"
 // "insert_text" handler for GtkEntry
 static void
 wx_gtk_insert_text_callback(GtkEditable *editable,
-                            const gchar *new_text,
-                            gint new_text_length,
-                            gint *position,
+                            const gchar * WXUNUSED(new_text),
+                            gint WXUNUSED(new_text_length),
+                            gint * WXUNUSED(position),
                             wxTextEntry *text)
 {
     // we should only be called if we have a max len limit at all