Add codes for DWARF v5 .dwp sections to dwarf2.h.

Add codes for DWARF v5 .dwp sections to dwarf2.h.

(Note: This patch has already been accepted/committed in binutils/GDB.
This will bring the same change into the GCC tree.)

For DWARF v5 Dwarf Package Files (.dwp files), the section identifier encodings
have changed. This patch updates dwarf2.h to contain the new
encodings.  The table below shows the old & new encodings:
[ref http://dwarfstd.org/doc/DWARF5.pdf, section 7.3.5. ]

Val  DW4 section       DW4 section id  DW5 section         DW5 section id
--- -----------------  --------------  -----------------   --------------
 1  .debug_info.dwo    DW_SECT_INFO    .debug_info.dwo     DW_SECT_INFO
 2  .debug_types.dwo   DW_SECT_TYPES         --              reserved
 3  .debug_abbrev.dwo  DW_SECT_ABBREV  .debug_abbrev.dwo   DW_SECT_ABBREV
 4  .debug_line.dwo    DW_SECT_LINE    .debug_line.dwo     DW_SECT_LINE
 5  .debug_loc.dwo     DW_SECT_LOC     .debug_loclists.dwo DW_SECT_LOCLISTS
 6  .debug_str_offsets.dwo             .debug_str_offsets.dwo
                       DW_SECT_STR_OFFSETS                 DW_SECT_STR_OFFSETS
 7  .debug_macinfo.dwo DW_SECT_MACINFO .debug_macro.dwo    DW_SECT_MACRO
 8  .debug_macro.dwo   DW_SECT_MACRO   .debug_rnglists.dwo DW_SECT_RNGLISTS

2020-09-09  Caroline Tice  <cmtice@google.com>

include/

	* dwarf2.h (enum dwarf_sect_v5): A new enum section for the
	sections in a DWARF 5 DWP file (DWP version 5).