Print stack trace instead of just source code line

[ingomueller-net]

With functions and modules that may be (transitively) called from several places in the query, it would be very useful to provide a stack trace instead of just the source code location of the top stack frame. Otherwise, the different possible calls to the location where the error occurs are indistinguishable.

A more involved solution might also provide variable bindings, maybe even for all stack frames.