New dev bundle: mongo with startup speed boost.

Also upgrade to 2.4.8 while we're at it.

(In the meteor/mongo repository, we've created an ssl-2.4.8 branch, and
also added a backported-from-Mongo-2.5 change to poll the repl set
config more often on startup.)
Upgrade to stock Node 0.10.22.

This discards our fix for stream pausing. We'll monkey patch it in
at startup instead of relying on a custom build.
Preemptively add bcrypt to the dev bundle. We think we may want it soon.
Use smaller oplog (8MB instead of 256MB default).

This uses less space on disk and starts up faster. It might mean
people hit the end of the oplog if the server gets really slow.
But, hey, then we can debug and test more oplog error modes.
Work around Node issue #6506.

We were previously doing this with a fork of Node in the dev bundle, but
that wouldn't help users in production.

We now expect users to use precisely v0.10.22 in production. When new
versions of Node come out, if users choose to use them before we get a
chance to put out a new Meteor, we disable websockets to work around the
most common effect of the issue instead of monkey-patching.
Fix find_mongo_pids regexp

Also add some comments to mongod options.
Merge branch 'mongo-startup-speedup' into devel