[Perl/perl5] bd90fa: sv.h - encode the misc SV_* flags using bitshifts

[Paul Evans via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: bd90fa412bb2eb27ffa23a0e439350a39847521e
      
https://github.com/Perl/perl5/commit/bd90fa412bb2eb27ffa23a0e439350a39847521e
  Author: Paul "LeoNerd" Evans <leon...@leonerd.org.uk>
  Date:   2023-02-08 (Wed, 08 Feb 2023)

  Changed paths:
    M sv.h

  Log Message:
  -----------
  sv.h - encode the misc SV_* flags using bitshifts

Using decimal integers is confusing, so we show the hex and
decimal values as a comment.

Note: Yves edited the commit message and added the commented
values.