[Bug libstdc++/78905] Add a macro to determine that the <regex> library is implemented

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78905

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |NEW
   Last reconfirmed|                            |2016-12-23
         Resolution|INVALID                     |---
   Target Milestone|---                         |8.0
     Ever confirmed|0                           |1
           Severity|normal                      |enhancement

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I asked for this to be created.