Don't use a splat with AST::Node#to_a
Don't use a splat with AST::Node#to_a

By using AST::Node#children directly with a splat we save ourselves an
extra method call. This in turn speeds up both the
xpath/evaluator/big_xml_average_bench.rb and
xpath/evaluator/node_matches_bench.rb benchmarks a little bit.

ttasanen/oga,YorickPeterse/oga,ttasanen/oga,altmetric/oga,jeffreybaird/oga,jeffreybaird/oga,ttasanen/oga,jeffreybaird/oga,dfockler/oga,altmetric/oga,ttasanen/oga,altmetric/oga,dfockler/oga,altmetric/oga,YorickPeterse/oga,ttasanen/oga,dfockler/oga,jeffreybaird/oga,dfockler/oga,altmetric/oga,jeffreybaird/oga,YorickPeterse/oga,YorickPeterse/oga,YorickPeterse/oga,dfockler/oga