fix, PEBKAC, only strdup the nick if non-NULL

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, temporarily use last_dsm to communicate whether it's a user nick or an auto nick

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, don't hand out nick names for symbols with NULL nick slot

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, clean up debugging output in sdef-twsxml

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'feat/nick' into next

* feat/nick:
  chore, clean up debugging output in sdef-twsxml
  minor, don't hand out nick names for symbols with NULL nick slot
  minor, temporarily use last_dsm to communicate whether it's a user nick or an auto nick
  fix, PEBKAC, only strdup the nick if non-NULL
Merge branch 'next'

* next:
  chore, clean up debugging output in sdef-twsxml
  minor, don't hand out nick names for symbols with NULL nick slot
  minor, temporarily use last_dsm to communicate whether it's a user nick or an auto nick
  fix, PEBKAC, only strdup the nick if non-NULL