[perl #133788] Make sv_utf8_downgrade() and sv_utf8_decode()non-unstable

# New Ticket Created by   
# Please include the string:  [perl #133788]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=133788 >


Hello, these two functions are currently marked as unstable with M in
embed.fnc function so they may change:

Apmdb   |STRLEN |sv_utf8_upgrade|NN SV *sv
Amd     |STRLEN |sv_utf8_upgrade_nomg|NN SV *sv
ApdM    |bool   |sv_utf8_downgrade|NN SV *const sv|const bool fail_ok
Apd     |void   |sv_utf8_encode |NN SV *const sv
ApdM    |bool   |sv_utf8_decode |NN SV *const sv

These functions are available since Perl 5.6.0 (just upgrade* since
5.7.2) and used by more XS modules on CPAN. AFAIK their API or behavior
was not changed so I suggest to remove M and make them "stable".

Or is there any specific reason why upgrade and encode is without M and
downgrade and decode with M?

• [perl #133788] Make sv_utf8_downgrade() and sv_utf8_decode()non-unstable by Tony Cook via RT
• [perl #133788] Make sv_utf8_downgrade() and sv_utf8_decode()non-unstable by perlbug-followup