Closes GH-604.

These are options needed for real-world multicasting.

Implementation notes:
- POSIX only.
- IPv4 only (IPv6 multicast is a tricky beast).
- Didn't update tests, because it can't effectively be demonstrated on
  localhost only.

See http://code.google.com/p/v8/issues/detail?id=884

See http://code.google.com/p/v8/issues/detail?id=884

This reverts commit 6dbf4911.

Introduced in f9f0e5c7

Closes GH-579.

Closes GH-586.

Thanks Kevin. Closes GH-518.

Closes GH-557.
Closes GH-539.

Thanks Bjarki. Closes GH-561.

Thanks Pierre. Closes GH-571.

require('./foo/') should not try to load './foo.js'.  It should only
look for ./foo/index.js

Closes GH-588