Fix the race condition in endpoint connection initialization. The race
was quite subtle, and only happened on the process with the smallest
guid (as this process will tear down the connection created locally and
replace it with the result of accept). If multiple threads are active in
the system, the deadlock occurs during the recv event deletion as one
thread will hold the recv event lock of the endpoint and try to access
the TCP event base lock, while the other thread will hold the TCP event
base lock while trying to access the recv event lock (in case data is
available on the socket).

The proposed solution let the event callback fail to process the data,
preventing the deadlock and allowing the other thread to always complete
it's job. As the event is not execute the same triggered will trigger
again at the next opportunity, so this solution introduce a minimal
delay in the connection establishement.
Add the necessary infrastructure to allow the dumping of all TCP
informations related to an endpoint (status and all pending fragments).
Do some minor space cleanup.
Correctly propagate the requested level of thread support during the
component init calls.
opal: minor update to guess_strlen

This is a minor update to
open-mpi/ompi@c52601f0c563132284cd1444c7a7039ba0032872.

If we have vsnprintf(), we might as well not have the rest of the
guess_strlen() routine.  Also document the nifty trick/behavior of
vsnprintf() that enables this shortcut (it was new to me!).