* lto-streamer-out.c (lto_string_index): break out from...; offset by 1
	so 0 means NULL string.
	(lto_output_string_with_length): ... here.
	(lto_output_string, output_string_cst, output_identifier): Update handling
	of NULL strings.
	(lto_output_location_bitpack): New function.
	(lto_output_location): Use it.
	(lto_output_tree_ref): Use output_record_start.
	(pack_ts_type_common_value_fields): Pack aliagn & alias set in var len values.
	* lto-streamer-in.c (string_for_index): Break out from ...; offset values by 1.
	(input_string_internal): ... here; 
	(input_string_cst, input_identifier, lto_input_string): Update handling of
	NULL strings.
	(lto_input_location_bitpack): New function
	(lto_input_location): Use it.
	(unpack_ts_type_common_value_fields): Pack align & alias in var len values.
	* lto-streamer.h (bp_pack_val_len_unsigned, bp_pack_val_len_int,
	bp_unpack_val_len_unsigned, bp_unpack_val_len_int): Declare.
	(bp_pack_value): Sanity check the value range.
	* lto-section-in.c (bp_unpack_val_len_unsigned, bp_unpack_val_len_int):
	New functions.
	* lto-section-out.h (bp_pack_val_len_unsigned, bp_pack_val_len_int):
	New functions.

From-SVN: r174325