I forgot that two of the case changing functions were already documented;
so the change in 5.19.1 is to add documentation for more.
=item *
XS code may use various macros to change the case of a character or code
-point (for example C<toLOWER()>). These weren't documented until now;
+point (for example C<toLOWER_utf8()>). Only a couple of these were
+documented until now;
and now they should be used in preference to calling the underlying
functions. See L<perlapi/Character case changing>.