gdb: print more data for segment events

gdb: print more data for segment events

This add the different timestamps for segment events:

(gdb) gst-print pad
SrcPad(src, push) {
  events:
[...]
    segment: time
      rate: 1.1
      start:    0:03:08.449753330
      time:     0:03:08.449753330
      position: 0:03:08.449753330
      duration: 0:12:14.166687500
[...]
}