[Free42] RTN Stack Full

[Thomas Okken]

I should point out that the RTN stack in Free42 and Plus42 is dynamic, so it's not a fixed 1024-entry array, and it could be allowed to grow to more than 1024 levels. The reason I put in the 1024-level limit is to provide a graceful failure mode for programs with infinite recursion bugs.

I could make the limit user-configurable, but there hasn't seemed to be a reason to do so yet.