[Bug libstdc++/71073] New: debug-mode headers should include #pragma GCC system_header directives

[froydnj at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71073

            Bug ID: 71073
           Summary: debug-mode headers should include #pragma GCC
                    system_header directives
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: froydnj at gcc dot gnu.org
  Target Milestone: ---

This change would help analysis tools cope with the code in the debug-mode
headers, usually by ignoring it.