WPrefs.app: Added const attribute to local string

Now that the WINGs functions are const-correct, it is possible to
set the attribute on the strings to help the compiler.

WPrefs.app/Expert.c

@@ -25,7 +25,7 @@
  * expert tab of the window with the corresponding information for effect
  */
 static const struct {
-	char *label; /* Text displayed to user */
+	const char *label;  /* Text displayed to user */
 
 	int def_state;  /* True/False: the default value, if not defined in current config */
 

WPrefs.app/KeyboardShortcuts.c

@@ -67,11 +67,7 @@ typedef struct _Panel {
  */
 static const struct {
 	const char *key;
-	/*
-	 * Fixme: this string should be 'const', but 'WMAddListItem'
-	 *        do not allow us to do so
-	 */
-	char *title;
+	const char *title;
 } keyOptions[] = {
 	{ "RootMenuKey",    N_("Open applications menu") },
 	{ "WindowListKey",  N_("Open window list menu") },