UPGRADE: packs mpr
REFACTOR:

Change how yield is performed. Goals:

- Make list of APIs yielding a small explicit set of APIs
- Remove recursion with httpProtocol
- Fix mixed calls to httpFinalize and httpFinalizeOutput

Changes
- Add API: httpClientConn, httpServerConn
- Add: httpRequestExpired
- Add blocking arg to httpServiceQueues
- Remove httpCloseConn
- Rename httpEvent to httpIOEvent (users should not be calling)
- Improve shutdown sequence
- Add httpStealConnHandle
- Rename httpStealConn to httpStealSocket
- Add httpSetEof
- Add httpNextQueueFull
- Rename httpPump to httpProtocol