Import include/+libiberty/ r249883 from upstream GCC.
    
    include/ChangeLog
    2017-07-02  Jan Kratochvil  <jan.kratochvil@redhat.com>
    
    	* dwarf2.def (DW_IDX_compile_unit, DW_IDX_type_unit, DW_IDX_die_offset)
    	(DW_IDX_parent, DW_IDX_type_hash, DW_IDX_lo_user, DW_IDX_hi_user)
    	(DW_IDX_GNU_internal, DW_IDX_GNU_external): New.
    	* dwarf2.h (DW_IDX, DW_IDX_DUP, DW_FIRST_IDX, DW_END_IDX): New.
    	(enum dwarf_name_index_attribute): Remove.
    	(get_DW_IDX_name): New declaration.
    
    libiberty/ChangeLog
    2017-07-02  Jan Kratochvil  <jan.kratochvil@redhat.com>
    
    	* dwarfnames.c (DW_FIRST_IDX, DW_END_IDX, DW_IDX, DW_IDX_DUP): New.