* objcopy.c (enum strip_action): Define strip_unneeded.

	* objcopy.c (enum strip_action): Define strip_unneeded.
	(OPTION_STRIP_UNNEEDED): Define.
	(strip_options): Add "strip-unneeded".
	(copy_options): Likewise.
	(copy_usage): Mention --strip-unneeded.
	(strip_usage): Likewise.
	(is_strip_section): Strip debugging sections if strip_unneeded.
	(filter_symbols): If strip_unneeded, only keep BSF_KEEP symbols.
	(copy_object): If strip_all, discard symbols without checking
	discard_locals.
	(copy_object): Call filter_symbols if strip_unneeded.
	(setup_section): Strip debugging sections if strip_unneeded.
	(copy_section): Likewise.
	(strip_main): Handle OPTION_STRIP_UNNEEDED.
	(copy_main): Likewise.
	* binutils.texi, objcopy.1, strip.1: Document --strip-unneeded.
PR 6684.