Print the default for all binary options; clean up --help output.

Print the default for all binary options; clean up --help output.

gold/
	PR gold/20346
	* options.cc (One_option::print): Print "(default)" when appropriate.
	* options.h: Clean up and re-sort options.
	(One_option::is_default): New data member.
	(One_option::One_option): Add is_default parameter; adjust all calls.
	(DEFINE_var): Add is_default__ parameter; adjust all calls.
	(DEFINE_bool): Set is_default based on default_value__.
	(DEFINE_bool_ignore): New macro.
	(--no-eh-frame-hdr): New option.
	(--enable-new-dtags): Remove mention of DT_FLAGS.