Changes to make -Ur work again.

	Changes to make -Ur work again.
	* ldmain.c (add_to_set): Now takes reloc argument rather than
	bitsize.  Check config.build_constructors here.  If an new hash
	table entry is created, mark it as undefined.
	(constructor_callback): No longer takes bitsize argument.  Pass
	BFD_RELOC_CTOR to ldctor_add_set_entry, but first make sure the
	BFD backend supports it.
	(reloc_overflow): Handle a NULL abfd argument.
	(reloc_dangerous, unattached_reloc): Likewise.
	* ldctor.c: Include ldmain.h.
	(struct set_info): Change bitsize field to reloc.
	(ldctor_add_set_entry): Now takes reloc argument rather than
	bitsize.  Don't bother to check config.build_constructors here.
	(ldctor_build_sets): Get the size from the reloc howto.  If
	generating relocateable output, call lang_add_reloc rather than
	lang_add_data.
	* ldctor.h (ldctor_add_set_entry): Change declaration to use reloc
	instead of bitsize.
	* ldlang.h (statement_enum): Add lang_reloc_statement_enum.
	(lang_reloc_statement_type): New structure.
	(lang_statement_union_type): Add reloc_statement field.
	(lang_add_reloc): Declare new function.
	* ldlang.c (lang_for_each_statement_worker): Handle
	lang_reloc_statement_enum.
	(map_input_to_output_sections, print_statement): Likewise.
	(lang_size_sections, lang_do_assignments): Likewise.
	(print_reloc_statement): New function.
	(lang_add_reloc): New function.
	* ldwrite.c (build_link_order): Handle lang_reloc_statement_enum.