* addr2line.c (usage): Document @file.

	* addr2line.c (usage): Document @file.
	* ar.c (usage): Likewise.
	* coffdump (usage): Likewise.
	* cxxfilt.c (usage): Likewise.
	* dlltool.c (usage): Likewise.
	* dllwrap.c (usage): Likewise.
	* nlmconv.c (usage): Likewise.
	* nm.c (usage): Likewise.
	* objcopy.c (usage): Likewise.
	* objdump.c (usage): Likewise.
	* readelf.c (usage): Likewise.
	* size.c (usage): Likeise.
	* srconv.c (usage): Likewise.
	* strings.c (usage): Likewise.
	* windres.c (usage): Likewise.
	* doc/binutils.texi: Add section on common options.