Fix `A.new([[1,2],3]).flatten` to return `Array`.
MODIFY
mrbgems/mruby-array-ext/mrblib/array.rb
mrbgems/mruby-array-ext/mrblib/array.rb
@@ -209,7 +209,7 @@ class Array
# a.flatten(1) #=> [1, 2, 3, [4, 5]]
#
def flatten(depth=nil)
- res = dup
+ res = Array.new(self)
res.flatten! depth
res
end

Fix `A.new([[1,2],3]).flatten` to return `Array`.