* dwarf2.c (struct line_info): Add member END_SEQUENCE to keep
        track of end_sequence markers.
        (add_line_info): Add END_SEQUENCE arg.
        (decode_line_info): Don't try to infer lo_pc and hi_pc from the
        debug-line info---it doesn't work right if a compilation unit
        consists of multiple discontiguous code-sequences.  It would be
        worthwhile to optimize for the common case where a compilation
        unit results in a contiguous set of code sequences, but this is
        quite tricky to get right for arbitrary DWARF2 files.
        (lookup_address_in_line_info_table): Don't use the last line entry
        for a compilation unit for anything with an address higher than
        this line entry.  Also, check for end_sequence markers to
        correctly handle discontinuities.
        (_bfd_dwarf2_find_nearest_line): When checking previously loaded
        compilation units, check all compilation units with each->high==0
        just like when reading compilation units.
        * dwarf2.c (decode_line_info): Initialize table->files and
        table->last_line to NULL to avoid segfaults due to random
        values in these members.
        (concat_filename): Check for out-of-range file number before
        indexing filename table.  Segfaults suck.
        * dwarf2.c (decode_line_info): Don't truncate address to least
        significant 32 bits (breaks 64 bit targets).
        (lookup_address_in_function_table): Ditto.
        (comp_unit_contains_address): Ditto.