force genome index into memory

When starting bam2bam (worker or working master), we now touch the whole
index to make sure it is in RAM when the alignment process starts.  This
should remove the problem of timeouts before any work could be done.
plugged nasty memory leak

Ported to new stable ZMQ 3.2, cleaned up in the process, added a
sensible command line to the "worker" module, and finally plugged an
ugly leak in run_io_multiplexor, that would show up in networked
operation.