examples/hiperfifo.c: improved

 * use member struct event’s instead of pointers to alloc’d struct
   events

 * simplify the cases for the mcode_or_die() function via macros;

 * make multi_timer_cb() actually do what the block comment says it
   should;

 * accept a “stop” command on the FIFO to shut down the service;

 * use cleaner notation for unused variables than the (void) hack;

 * allow following redirections (304’s);