Add enough support to understand the gcc svr3.ifile script:

	Add enough support to understand the gcc svr3.ifile script:
	* ldlex.l: Recognize BLOCK and GROUP in EXPRESSION context.  Add
	BIND keyword.
	* ldgram.y: Add BIND token.
	(section): Recognize GROUP.
	(opt_ext_with_type): Recognize a couple of cases of BIND.
	* ldlang.c (init_os): Don't do anything if section is already
	initialized.  Call exp_init_os on addr_tree field.
	(exp_init_os): New static function.
	(map_input_to_output_sections): Call exp_init_os on assignment
	expression.
	(lang_place_orphans): Check for common sections by name COMMON
	rather than by common_section field.  Don't warn about absence of
	[COMMON] command.