Add misc:spawn_monitor/1 function.
Add misc:spawn_monitor/1 function.

This is a rough analogue to what would be
proc_lib:spawn_monitor/1. But unfortunately the latter doesn't
exist.

Change-Id: I71b86d3a8aedcfe343ea5c4180cba47713c162e6
Reviewed-on: http://review.couchbase.org/86384
Reviewed-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>
Well-Formed: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Tested-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>

membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server