are correctly assumed Perl unicode strings, instead of relying on its
internal character encoding as UTF-8.
This *might* break (potentially broken) apps that passes UTF-8 encoded
strings, instead of decoded strings, to ->execute or ->bind_param()
without SQL_BLOB. But this new behavior is more natural to how Perl
handles strings and consisten to what other drivers do under UTF-8
options set, e.g. DBD::mysql with mysql_enable_utf8 option. See also
http://use.perl.org/~miyagawa/journal/38770 for details.
Fixes RT bug 25371.