This function carries out networked (blocked) activity
for outstanding requests which have been prepared by the
functions yaz_connect(),
yaz_search(), yaz_present(),
yaz_scan() and
yaz_itemorder(). yaz_wait() returns when all targets have
either completed all requests or aborted (in case of
errors).
If the options array
is given that holds options that change the behaviour of yaz_wait().
Sets timeout in seconds. If a target hasn't
responded within the timeout it is considered dead and
yaz_wait() returns. The default
value for timeout is 15 seconds.