Introducing I/O reactor in UDP listeners
Timer jobs are dispached via reactor to all workers.

Instead of running the timer jobs in dedicated timer processes, now we simply dispatche the jobs to all SIP workers processes.
Still need some working on priorities.
TCP workers still not running the "SIP worker" reactor, so no timer jobs in these processes for the moment.
Add generic reactor support for the TCP processes.

"extra_loop" instruction can be forced in reactor to be executed in the loop;
TCP procs code migrated to the generic reactor;
FD del functions added to the reactor;
Timer jobs now also handled by the TCP processes;
Timer system must be init after daemonize !!
Reactors have names, easier for debugging purposes.
Removed the concept of timer routine per process.

This makes nosense now as the timer routines are dispatched across all the worker processes.
Version increased from 1.12 to 2.1 for MASTER