Fixes #1516.

Fixes #1888.

A class with virtual methods should have a virtual destructor.

Only register once for listening when passing a callback to Server.listen(),
this prevents servers recycled using close() from invoking the callback when
Server.listen() is called later.

On platforms that support it: linux, freebsd, darwin

Fixes #1644

Reading of JSON data off the buffer, 10-15% performance increase.

Fixes #1864.

Use process.argv instead.

Some of the perf improvements from many-writes-fix branch were accidentally
undone in that commit. This puts them back in.

Fixes #1869.

fs.readdir() on file should raise ENOTDIR, not UNKNOWN.