Fix compiler warning about different signedness of pointers in editcmd.c

Signed-off-by: Patrick Winnertz <winnie@debian.org>

edit/editcmd_dialogs.h

@@ -14,7 +14,7 @@ struct etags_hash_struct;
 /*** structures declarations (and typedefs of structures)*****************************************/
 
 struct selection {
-    unsigned char *text;
+    gchar *text;
     int len;
 };