* freebsd.h: New file.
	* i386.cc: Include "freebsd.h".
	(Target_i386): Derive from Target_freebsd rather than
	Sized_target.
	(Target_selector_i386): Derive from Target_selector_freebsd rather
	than Target_selector.
	* x86_64.cc: Include "freebsd.h".
	(Target_x86_64): Derive from Target_freebsd rather than
	Sized_target.
	(Target_selector_x86_64): Derive from Target_selector_freebsd
	rather than Target_selector.
	* target.h (class Target): Add adjust_elf_header and
	do_adjust_elf_header.
	* output.cc (Output_file_header:: do_sized_write): Call target
	adjust_elf_header routine.
	* configure.tgt: Set targ_osabi.
	* configure.ac: Define GOLD_DEFAULT_OSABI.
	* parameters.cc (Parameters::default_target): Pass
	GOLD_DEFAULT_OSABI to select_target.
	* target-select.h (class Target_selector): Make instantiate_target
	protected rather than private.
	* Makefile.am (HFILES): Add freebsd.h.
	* configure, Makefile.in, config.in: Rebuild.