doc: remove note about close event
http: use socket.once, not socket.on

Register the 'close' event listener with .once(), not .on().

It doesn't matter in the grand scheme of things because the listener
doesn't keep references to any heavy-weight objects but using .once()
for a oneshot listener is something of a best practice.
blog: Post about v0.9.11
crypto: don't assert when calling Cipher#final() twice

Remove the assert() that triggered when Cipher#final() or
Decipher#final() was called twice.

Fixes #4886.
test: optionally set common.PORT via env variable

This is a back-port of commit 17a8126 from the master branch.
test: make simple/test-dgram-pingpong respect PORT

Don't use hard-coded port numbers, use common.PORT instead.

Should fix the occasional Jenkins failure; the builds run in parallel.
Merge remote-tracking branch 'origin/v0.8'

Conflicts:
	doc/api/http.markdown
	test/simple/test-crypto.js
events: Handle emit before constructor call