The correct upstream bug is https://sourceware.org/bugzilla/show_bug.cgi?id=21792 which has been resolved for the 0.170 release:

Although it isn't full DWARF5 support all DWARF5 tags and attributes are recognized in 0.170. From the NEWS file:

Version 0.170

libdw: Added new DWARF5 attribute, tag, character encoding, language code,
       calling convention, defaulted member function and macro constants
       to dwarf.h.
       New functions dwarf_default_lower_bound and dwarf_line_file.
       dwarf_peel_type now handles DWARF5 immutable, packed and shared tags.
       dwarf_getmacros now handles DWARF5 .debug_macro sections.

And the above example now shows:

 [   7e1]      namespace
               name                 (strp) "__cxx11"
               decl_file            (data1) 1
               decl_line            (data2) 2214
               export_symbols       (flag_present) yes

Rebase testing finished with elfutils-0.170-4.el7.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHEA-2018:0891