Merge branch 'bugfix/detect_ocd_when_panic' into 'master'

Fix OpenOCD detection code

In the current master, detection of an attached OCD is broken. This fixes it.

I also snuck in two unrelated checks in intr_alloc which return from a function that is asserted earlier in the code. This makes the code behave better when they are called erroneously in a production build.

See merge request !377