dwarf2out.c (dw_ranges_by_label_ref): New typedef.

* dwarf2out.c (dw_ranges_by_label_ref): New typedef.
(dw_ranges_struct): Rename block_num to num.  Adjust.
(dw_ranges_by_label_struct): New.
(ranges_by_label, ranges_by_label_allocated,
ranges_by_label_in_use): New variables.
(add_ranges_num): Factored most of the code out of...
(add_ranges): ... this one.  Rewrite in terms of the former.
(add_ranges_by_labels): New.
(output_ranges): Output by-label ranges.
(dwarf2out_finish): Output range for multiple-section
compile_unit.  Output standard DW_AT_low_pc in addition to
unexpected DW_AT_entry_pc.

From-SVN: r126357