Merge pull request #3 from jussy/master

Use scoped lock inside mac-specific XrdSysSemaphore implementation to avoid deadlock on thread cancellation
[XrdCl] Add possibility to have raw outgoing message handlers
[XrdCl] Implement direct buffer writing

Get rid of the time spent in memcpy+memset, witch was 97% of usertime.
[XrdCl] Prevent error messages from being truncated when failing requests queued for recovery
[XrdClient] Properly add opaque destination data
Add new scaled number convertor for future use.
[XrdCl] Allow for memory ownership management of the TaskManager tasks
[XrdCl] Expose the JobManager in PostMaster
[XrdCl] Default the job argument to 0 in JobManager::QueueJob
[XrdCl] Handle timeouts for stateful file requests while in the recovery mode
Avoid lock inversion when handling the timeout queue in the presence of
a timeout callback. This may cause a deadlock.
Update notes for event deadlock patch.
[XrdCl] Clean up the memory after executing the response job
[XrdCl] Poller errors are fatal
[XrdCl] Fix a comment
[XrdCl] Recover stateful requests only on network errors
[XrdCl] Make sure to recover only when recovery is enabled
[XrdCl] Add interface to suppoort stream control messages
[XrdCl] Digest an XRootD message if nobody is waiting for it
[XrdCl] Use XrdSysTimer instead of sleep to avoid tight loops (interrupts)