Change S-record backend to use multiple sections to handle gaps in

	Change S-record backend to use multiple sections to handle gaps in
	file.
	* srec.c (srec_data_list_struct): Move field next from last place
	to first.  Change type of data to bfd_byte *.
	(struct srec_symbol): Define.
	(tdata_type): Remove done_symbol_read, count, strings, symbol_idx,
	string_size, string_idx.  Change type of symbols to struct
	srec_symbol *.  Add symtail and csymbols.
	(low, high): Remove.
	(size_symbols, fillup_symbols, size_srec, fillup): Remove.
	(white, skipwhite, pass_over, object_p): Remove.
	(srec_mkobject): Call srec_init.  Adjust tdata initialization for
	field changes.
	(srec_get_byte, srec_bad_byte): New static functions.
	(srec_new_symbol, srec_scan): New static functions.
	(srec_object_p): Change type of b to bfd_byte.  Explicitly set
	wrong_format error.  Call srec_mkobject and srec_scan instead of
	object_p.
	(symbolsrec_object_p): Likewise.  Also, change b to be only two
	bytes.
	(srec_read_section): New static function.
	(srec_get_section_contents): Call srec_read_section rather than
	pass_over.  Handle zero length section correctly.
	(set_set_arch_mach): Change from function to macro.
	(srec_set_section_contents): Change data to bfd_byte *.
	(srec_write_record): Change data, end and src to bfd_byte *.
	(srec_write_header): Change buffer and dst to bfd_byte *.
	(srec_write_section): Change location to bfd_byte *.
	(srec_write_terminator): Change buffer to bfd_byte *.
	(srec_get_symtab_upper_bound): Don't call
	srec_get_section_contents.
	(srec_get_symtab): Rewrite.