dwarf2out.c (AT_flag, [...]): Abort on unsuitable input.

        * dwarf2out.c (AT_flag, AT_int, AT_unsigned, AT_string, AT_ref,
        AT_loc, AT_addr, AT_lbl): Abort on unsuitable input.
        (get_AT_low_pc, get_AT_hi_pc, get_AT_string, get_AT_flag,
        get_AT_unsigned, get_AT_ref): Don't call them if get_AT fails.

From-SVN: r35953