bson.reader: Allow reading a sequence of bson objects from a file.
build-support: Install screen and tmux with apt-get/pacman.
I want this to work out of the box on a new build farm machine.
build-support: Install libssl on ubuntu.
io.sockets.secure.openssl: libssl error is opaque, check that cert files
exist in Factor beforehand so we can get a nicer error message.
Add missing USE: and neaten up the list.
alien.libraries.finder.linux: dont use dlopen.
alien.libraries.finder.windows: more like MSDN search order.