Impala code refresh v0.4 (pre-release version) -> v0.4

* Fix hdfs-scan-node deadlock.

  row_batches_lock_ should be taken after lock_. But in this bug, we took
  row_batches_lock_ first.

* Fix race condition due to misuse of shared_ptr in StreamControlBlock.
* Removing uses of perf-counters code (will not work on RHEL 5 kernel)
* Fix race condition in opcode registry initialize.
* Add CURRENT_TIMESTAMP() function as synonym for now()
* Fix leak of open hdfs files during cancellation.
* Fix race condition in scanners/scan-node.
* Fix hang for queries when the limit is first reached by the coordinator.

  Remote fragments are waiting for the coordinator to pump rows but the coordinator
  decided it was done.  This caused remote fragments to hang.  The coordinator was
  in turn waiting for the remote fragments to finish.

* Improved metrics for tracking impalad resource utilization.
* Move sparrow/ to statestore/ and remove sparrow namespace
* Added start/end query time to debug webpage.
* Add build option to enable address sanitizer.
* impala-shell calls PingImpalaService thrift API to verify the server is an impalad.
* IMPALA-14: Files with .gz extension reported as 'not supported'
* Use recompiled, relocatable static libraries when they are available