add error::code() that returns libuv error code; add ctor that accepts libuv error code
add error::code() that returns libuv error code; add ctor that accepts libuv error code

chenmoshushi/node.native,mattn/node.native,sebjameswml/node.native,supamii/QttpServer,supamii/QttpServer,sebjameswml/node.native,nodenative/nodenative,d5/node.native,8l/node.native,supamii/QttpServer,8l/node.native,mattn/node.native,chenmoshushi/node.native,8l/node.native,nodenative/nodenative,d5/node.native,supamii/libuv.qt,supamii/QttpServer,supamii/libuv.qt,supamii/libuv.qt,sebjameswml/node.native,nodenative/nodenative,supamii/QttpServer,supamii/QttpServer,takano32/node.native,chenmoshushi/node.native,takano32/node.native,supamii/libuv.qt,d5/node.native