* dwarf2dbg.c: Rewrite from scratch. Queue all debugging output

    * dwarf2dbg.c: Rewrite from scratch.  Queue all debugging output
        until dwarf2_finish; use relaxation to get cross-fragment offsets;
        thread multiple subsegments properly; handle multiple code
        sections properly; emit proper compilation unit info for assembler
        generated debugging.

        * as.h (enum _relax_state): Add rs_dwarf2dbg.
        * dwarf2dbg.h (struct dwarf2_line_info): Remove filename.
        (dwarf2dbg_estimate_size_before_relax): Declare.
        (dwarf2dbg_relax_frag, dwarf2dbg_convert_frag): Declare.
        * write.c: Include dwarf2dbg.h.
        (cvt_frag_to_fill): Handle rs_dwarf2dbg.
        (relax_segment): Likewise.