Fix for 1073532: Mo doesn't work with Scalar::Util::PP

Unlike Scalar::Util, Scalar::Util::PP::looks_like_number shifts @_,
so calling it as &looks_like_number works differently in both
versions; see https://rt.cpan.org/Public/Bug/Display.html?id=80525

t/lib/Mo/isa_subtest.pm

@@ -0,0 +1,28 @@
+BEGIN {
+   require Scalar::Util::PP;
+   *Scalar::Util:: = \*Scalar::Util::PP::;
+   $INC{"Scalar/Util.pm"} = __FILE__;
+};
+
+BEGIN {
+   die "The PERCONA_TOOLKIT_BRANCH environment variable is not set.\n"
+      unless $ENV{PERCONA_TOOLKIT_BRANCH} && -d $ENV{PERCONA_TOOLKIT_BRANCH};
+   unshift @INC, "$ENV{PERCONA_TOOLKIT_BRANCH}/lib";
+};
+
+use strict;
+use warnings;
+
+{
+   package isa_subtest;
+   use Mo;
+
+   has attr => (
+      is  => 'rw',
+      isa => 'Int',
+   );
+
+   1;
+}
+
+isa_subtest->new(attr => 100);