Bug Fixes

• Fix server to shutdown when alive connections exist
  (by @ciscorn in 5f71e29 for #180 in PR #181)

• Fix a few bugs and crashes in UDP layer
  (by @1st1 in e0b5ea0, 5eef2d5 for #190)

• Fix FD leakage if spawning a subprocess fails
  (by @1st1 in 4f6621e for #185, #186)

• Fix libuv process handles leak when uv_spawn() fails
  (by @1st1 in 92ea517 for #187)