This adds an inter-thread queue "it_q" to libosmocore. With it_q,
one can perform thread-safe enqueing of messages to another thread,
who will receive the related messages triggered via an eventfd
handled in the usual libosmocore select loop abstraction.
Change-Id: Ie7d0c5fec715a2a577fae014b0b8a0e9c38418ef
