Updated gems_list.txt.
Make JIT inline cast_for_multi_block_arg correctly

JIT was not inlining arguments correctly when given more than one
argument, and would end up yielding cUndef (Object:0x22) instead.

See https://gist.github.com/sshao/7eecc87458d3e55d7f5d for examples.
Fixed JIT calling rbx_instance_of.
Added specs for IO.new with closed IO streams.
Added checks in IO.new for closed IO streams.