shib-threads.{h,cpp}:

shib-threads.{h,cpp}:
	added Thread::mask_signal() function to mask around pthread_sigmask()
	(couldn't call it sigmask() because that's a macro)

shar-utils.cpp:
shib-ccache.cpp:
	block all signals in children threads, to make sure they don't
	(improperly) handle signals, such as at SHAR Shutdown.

git-svn-id: https://svn.middleware.georgetown.edu/cpp-sp/trunk@257 cb58f699-b61c-0410-a6fe-9272a202ed29