Update to stunnel 4.11
The hack in patch-src::common.h is not needed anymore, because now
stunnel has --with-threads configure option.
patch-src::sthreads.c is also needless, stunnel's ucontext model now
includes it itself.
Over to maintainer.
Committed with slight modifications: PTHREAD_CFLAGS and PTHREAD_LIBS also
need to be added in the ucontext case, and they need to be added at the
proper stage of configuration.
Thanks for the update!