Properly tail recursive functions in VeLa

[dbenn]

Detecting and handling properly tail recursive functions, e.g. to allow loops.

Detection:

• final AST in function is a recursive call, or
• final select AST consequent is a recursive call

Thoughts:

• compiling VeLa would do it;
• continuation passing vs direct style combined with iteration;
• loop that invokes Java code that handled this: do...while(tailCall && !finished);
• need to detect leaf nodes in relevant part of AST (function, selection statement in function) that are calls to the currently activated function.