Support recover() for tracing source of a panic

[deniseli]

We recently encountered a panic in go-runtime/compile/schema.go (fix) triggered by the PFI code, but we were not able to easily identify exactly what line in PFI caused the panic. Alec suggested "we should have a recover() in the code that tracks the current node being parsed so we can report where the panic occurs. Something like defer catch(node)"