hygiene, refactor sorting routines to operate on struct sks_s objects

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, use bitset (pgbs of struct sks_s) to determine whether or not to load_run() a page

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, polish some diagnostics in utesort.c

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
fix, PEBKAC, drop runs even if there's no more strat nodes

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

* core/sort:
  fix, PEBKAC, drop runs even if there's no more strat nodes
  chore, polish some diagnostics in utesort.c
  minor, use bitset (pgbs of struct sks_s) to determine whether or not to load_run() a page
  hygiene, refactor sorting routines to operate on struct sks_s objects