read() performance is improved most by switching from an array to
a linked list for storing buffered data. However, other changes that
also contribute include: making some hot functions inlinable, faster
read() argument checking, and misc code rearrangement to avoid
unnecessary code execution.
PR-URL: https://github.com/nodejs/node/pull/7077
Reviewed-By: Calvin Metcalf <calvin.metcalf@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
