Support for typed laziness in executor
Regression test for infinite regress in executor

This test will fail if laziness doesn't prevent infinite recursion in
the executor. It's implemented using `expect` instead of `timeout` in
the hope that it will make life easier for non-GNU systems.
Normalise thunk contents when returning from executor
Merge pull request #1038 from david-christiansen/typed-lazy-executor

Support for typed laziness in executor