fix compile error for latest mruby and libuv-v0.10.19

This patch targets latest mruby(after mrb_intern API change) and libuv-v0.10.19 . 
The basic changes is:
* *mrb_intern* is replaced with *mrb_intern_lit*
* *uv_last_error* is used to get error value that will be passed to *uv_strerror*

In addition *uv_ip4_addr* and *uv_ip6_addr* code won't compile with current libuv master branch because it had a API change.