minor, update gq implementation to single-linked list only

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, adapt quo.c to new gq.[ch]

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, adapt sub.c to new gq.[ch]

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

* code/hygiene:
  minor, adapt sub.c to new gq.[ch]
  minor, adapt quo.c to new gq.[ch]
  minor, update gq implementation to single-linked list only