[Petal] Dereferencing SCALAR references correctly

[Warren Smith]

if you do this:

template.html
-------------
<div petal:content="vals/var1"></div>

program.pl
----------
$var1 = "Hello";
$var2 = "Hello2";

%vals = ( var1=>\$var1, var2=>\$var2);
$tpl = new Petal(...);
echo $tpl->process({vars => \@vals});

Hello and Hello2 are not set. you see SCALAR references.

Changing the last part of Petal/Hash/Var.pm to