compat send no SIGPIPE: multithread-safe

compat send no SIGPIPE: multithread-safe

The current implementation of the no-SIGPIPE send in the compatibility
layer has side-effects on multithreaded processes due to use of
sigaction(). Although multithread-safety is not strictly needed since
Babeltrace is single-threaded for now, there is no reason to keep this
limitation deeply rooted in a compatibility layer.

Use the multithreaded-safe algorithm to catch SIGPIPE implemented in
LTTng-UST for the write() system call for platforms that do not have
MSG_NOSIGNAL. It was originally implented in LTTng-UST as part of the
ring buffer wakeup. This is a re-implementation of this same algorithm
under MIT license. It uses signal masks and sigtimedwait.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>