[Bug c/92663] New: Add __gcc_has_bug or __gcc_bug_fixed

[fiesh at zefix dot tv]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92663

            Bug ID: 92663
           Summary: Add __gcc_has_bug or __gcc_bug_fixed
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fiesh at zefix dot tv
  Target Milestone: ---

The former, while logically sounder, seems difficult to implement without
adding every single open ticket on GCC's Bugzilla and returning `true` for
every non-existent one.

So probably the latter is a better choice.

It would allow code like

#if __gcc_bug_fixed(12345)
actual_code();
#else
workaround_code();
#endif

Of course ideally the array containing the fixed bugs' numbers would be filled
directly from Bugzilla's database, if possible.