A new OutputStream type- BufferedOutputStream is added in this patch.
All log messages going to this stream are appended to a log buffer.
Messages from this log buffer are read by a log thread which
appends messages to the data node log file.

The log buffer is of type LogBuffer- a class introduced in this
patch. LogBuffer handles the producer consumer problem.
Appending logs to the log buffer is always non-blocking.
Hence, the problems arising due to synchronous prints are avoided

The data node's worker process's log messages are made to go into the
BufferedOutputStream. This makes logging through ndbout << , ndbout_c,
g_eventLogger in the worker non-blocking.

Logging using [f]printf, [f]write are blocking/synchronous and must be avoided.

CPU locking of the log thread is akin to the other IO threads(Ndbfs).