Closes GH-640.

This adds basic support for situations where there is a package.json
with a "main" field.  That "main" module is used as the code that is
loaded when the package folder is required.

Patch by Marc Lehmann.
This fix should be included in the next libev release.

This reverts commit 25d0e380.

Re-enable test-https-large-response.js

Closes GH-614.

Also disable test-https-large-response.js. Covered by
test/simple/test-tls-throttle.js

Closes GH-613.

Closes GH-612.

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