Crashes on large signal trees #178

- Difficult to say whether this is actually caused by stack overflows (allthough it seems
  very likely)

- For now simply prepare further testing/verification: add the optimize and verification
  steps to all 'run' functions (RT and NRT) and a note about checking tree depth (requires
  walking the tree etc).

- Also add generic code to increase stack size (non-Windows), but do not use it yet.