gdb

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.