Force .join to reify at least 4 elements of a list (if available).

This should help with infinite lists that currently produce "..."
-- now it will at least produce the first four elements of such a list.

src/core/Any.pm

@@ -44,6 +44,7 @@ my class Any {
     method join($separator = '') {
         my $list = (self,).flat.eager;
         my Mu $rsa := pir::new__Ps('ResizableStringArray');
+        $list.gimme(4);        # force reification of at least 4 elements
         nqp::push_s($rsa, nqp::unbox_s($list.shift.Stringy)) 
             while $list.gimme(0);
         nqp::push_s($rsa, '...') if $list.infinite;