minor, import dt_strp() and dt_strf() from echse and dub instants trod_instant_t

Signed-off-by: Sebastian Freundt <freundt@fresse.org>
minor, import echse instant helpers and echs_instant_fixup() (as trod_instant_fixup())

Signed-off-by: Sebastian Freundt <freundt@fresse.org>
Merge branch 'feat/libtruffle' into next

* feat/libtruffle:
  minor, import echse instant helpers and echs_instant_fixup() (as trod_instant_fixup())
  minor, import dt_strp() and dt_strf() from echse and dub instants trod_instant_t