gsmopen: retry serial initialization if failed, zeroing audio buffers, slower retry on soundcard busy (EAGAIN)

         this should fix potential call_data pointer corruption

         this fixes a race where the call is hangup even before the state
         DIALING is processed and therefore the HANGUP state change is
         ignored.

add presence-probe-on-register sofia param to send a probe on register instead of presence to deal with some broken phones and add some general improvements to allow multi homed presence

                        have been cleared. This should fix issues with
                        state transitions being ignored.

FS-535:  fix issue in is_lan_addr where 172.2 would match 172.250.x.x which is not RFC1918 this also fixes an chicken egg issue

         if this parameter is set to 0 ftmod_analog will not wait
	 for dial tone before dialing out the requested number.
	 Anything bigger than 0 is the units in milliseconds to
	 wait for dialtone before aborting the call.