* targets.c (bfd_target): Add _bfd_read_ar_hdr field. Modify

	* targets.c (bfd_target): Add _bfd_read_ar_hdr field.  Modify
	BFD_JUMP_TABLE_ARCHIVE accordingly.
	* libbfd-in.h (_bfd_snarf_ar_hdr): Don't declare.
	(_bfd_compute_and_write_armap): Declare.
	(_bfd_generic_read_ar_hdr): Declare.
	(_bfd_read_ar_hdr): Define.
	(_bfd_noarchive_read_ar_hdr): Define.
	(_bfd_archive_bsd_read_ar_hdr): Define.
	(_bfd_archive_coff_read_ar_hdr): Define.
	* archive.c: Change all callers of _bfd_snarf_ar_hdr to call
	_bfd_read_ar_hdr instead.
	(_bfd_generic_read_ar_hdr): Rename from _bfd_snarf_ar_hdr.
	(_bfd_compute_and_write_armap): Rename from
	compute_and_write_armap.  Make non-static.  Change all callers.
	* ecoff.c (_bfd_ecoff_slurp_armap): Call _bfd_read_ar_hdr rather
	than _bfd_snarf_ar_hdr.
	* aout-target.h (MY_read_ar_hdr): Define if not defined.
	* ieee.c (ieee_read_ar_hdr): Define.
	* libecoff.h (_bfd_ecoff_read_ar_hdr): Define.
	* oasys.c (oasys_read_ar_hdr): Define.
	* som.c (som_read_ar_hdr): Define.
	* bfd-in2.h, libbfd.h: Rebuild.