Deal with blessed regexes

[aferreira]

Regex objects (like qr/Foo/) are kind of special in Perl
because they have a REGEXP reftype but are blessed into "Regexp"
package. That means it is not desirable to dump qr/Foo/ into

bless(qr/Foo/, "Regexp")

which is redudant, but if the blessed package is other than "Regexp"
it is necessary to resort to the "bless" expression, as in

bless(qr/Foo/, "Regexp::Alt")

Previous to this change, this was the output by Data::Dump for such cases:

perl -MData::Dump=pp -e 'pp(bless qr/Foo/, "Regexp::Alt")'
do {
  my $a = bless(do{\(my $o = do{my $fix})}, "Regexp::Alt");
  $$a = $a;
  $a;
}

From this change on, the output becomes

perl -MData::Dump=pp -e 'pp(bless qr/Foo/, "Regexp::Alt")'
bless(qr/Foo/, "Regexp::Alt")

which evaluates correctly and that follows what Data::Dumper
and Data::Dump::Streamer do.