chg: defer shutdown in slCleanUp() and slKill()
(cherry picked from commit 147e86a78bc224078ef082c481a0eed0a8600d7f)

Signed-off-by: Andreas Steenpass <steenpass@mathematik.uni-kl.de>
chg: messages about assign/conversion/calling: option(warn) -> TRACE

from master
Merge pull request #416 from steenpass/defer_shutdown_sw

chg: defer shutdown in slCleanUp() and slKill()
chg: make "=" for newstruct usable with >1 args on rhs
fix: default assignment for blackbox
chg: option(warn) changed