sigprocmask(2): pthread_sigmask(3) must be used in threaded processes. Although libthr's pthread_sigmask() just calls sigprocmask() and this is unlikely to change, mention this POSIX requirement on applications.
sigprocmask(2): pthread_sigmask(3) must be used in threaded processes.
Although libthr's pthread_sigmask() just calls sigprocmask() and this is
unlikely to change, mention this POSIX requirement on applications.

MFC after:	1 week

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase