Added regression test to verify that volatile expressions disable
inverse transition functions.
Removed trailing whitespace
Added test to exercise the restart-on-NULL behaviour for inverse transition functions.
Merge branch 'invtrans_base' into invtrans_minmax
Add some regression tests for max, min and bool_or and bool_and

(cherry-picked e1ebc8c876f55762c57b1b844f0d3487fc07a654)