t/safeuniversal.t failure under 5.8.9

t/safeuniversal.t failure under 5.8.9

[RT CPAN #48505]

The "no warnings 'redefined'" directives in the compartments
in t/safeuniversal.t cause test failures under 5.8.9 because
warnings.pm has a 'use Carp' directive and Carp.pm uses
'eval' to 'require Carp::Heavy'.

The attached patch replaces the "no warnings 'redefined'"
directive with a $SIG{__WARN__} trap for 5.8.9. While the
redefine warning for UNIVERSAL::can is suppressed by the
trap, the warning UNIVERSAL::isa still shows up. However,
the failing test will now pass under 5.8.9.