chg: update tasks.lib

Improve handling of internal data structures, especially intvecs.
(cherry picked from commit 091fbfe87825a276fac0079c772304a96a7cb118)

Signed-off-by: Andreas Steenpass <steenpass@mathematik.uni-kl.de>
Merge pull request #483 from steenpass/tasks_sw

chg: update tasks.lib