FS-8042, FS-8182: add ping time (in ms) to sip_registrations table, displays as part of the show commands that show registration details, add force_ping=true user var to force options ping on individual registered endpoints

src/mod/endpoints/mod_sofia/mod_sofia.h

@@ -181,6 +181,7 @@ struct sofia_private {
 	int destroy_me;
 	int is_call;
 	int is_static;
+	switch_time_t ping_sent;
 };
 
 #define set_param(ptr,val) if (ptr) {free(ptr) ; ptr = NULL;} if (val) {ptr = strdup(val);}