PR 10880

	PR 10880
	* object.h (class Object): Add is_needed and set_is_needed
	methods.  Add is_needed_ field.  Make bool fields into bitfields.
	* symtab.cc (Symbol_table::set_dynsym_indexes): If a symbol is
	defined in a dynamic object and referenced by a regular object,
	set is_needed for the dynamic object.
	* layout.cc (Layout::finish_dynamic_section): Don't add DT_NEEDED
	if the file is marked with as_needed and it is not needed.