Cloning the predicates and loop lists in the control directives inside the function evaluator. Necessary in case they get modified during the in-place evaluation.

Evaluating numeric constants as soon as possible (i.e., at parse time). Should prevent subtle eval bugs later on.

Little tweaks. Some concatenations are still erroneously quoted, but that can be easily worked around for the time being with the 'unquote' built-in.

Redoing the arithmetic. Should fix some erroneous behavior on complex expressions in weird contexts.

Conflicts:
	functions.cpp

Eh, not doing the cloning thing after all. If there's an error in the argument to a built-in function, just report the entire call site rather than the location of the argument.