Add private method devirtualizing to default opts.

src/Perl6/Optimizer.nqp

@@ -564,7 +564,7 @@ class Perl6::Optimizer {
 
         # If it's a private method call, we can sometimes resolve it at
         # compile time. If so, we can reduce it to a sub call in some cases.
-        elsif $*LEVEL >= 3 && $op.op eq 'callmethod' && $op.name eq 'dispatch:<!>' {
+        elsif $*LEVEL >= 2 && $op.op eq 'callmethod' && $op.name eq 'dispatch:<!>' {
             if $op[1].has_compile_time_value && nqp::istype($op[1], QAST::Want) && $op[1][1] eq 'Ss' {
                 my str $name := $op[1][2].value; # get raw string name
                 my $pkg  := $op[2].returns;  # actions always sets this