gdb

* symfile.c (reread_symbols): Don't pass argument to observer.
	* exec.c (exec_file_attach): Don't pass argument to observer.
	* ada-lang.c (ada_executable_changed_observer): Remove argument.
	* symtab.c (symtab_observer_executable_changed): Remove argument.
	* observer.sh: Handle functions with no arguments.
gdb/doc
	* observer.texi (GDB Observers): Remove obsolete comment.
	<executable_changed>: Remove argument.

gdb/symfile.c

@@ -2495,7 +2495,7 @@ reread_symbols (void)
       clear_symtab_users ();
       /* At least one objfile has changed, so we can consider that
          the executable we're debugging has changed too.  */
-      observer_notify_executable_changed (NULL);
+      observer_notify_executable_changed ();
     }
       
 }