This changes the prototype of uv_run() from:
int uv_run(uv_loop_t* loop);
To:
int uv_run(uv_loop_t* loop, uv_run_mode mode);
Where `mode` is UV_RUN_DEFAULT, UV_RUN_ONCE or UV_RUN_NOWAIT.
Fixes#683.
Demonstrates temporary event loop stall with uv-unix. The issue is that pending
requests aren't processed until the next event (I/O, timeout, etc.) happens.
See #446, #447 and #448.