Changed foreach to step the iterator after the loop instead of before it, so

that the iterator points to the current element instead of the next one.
Also some cleanup in iterators.cmod and a bit better error checking in
get_iterator.

Rev: src/builtin_functions.h:1.27
Rev: src/docode.c:1.166
Rev: src/interpret_functions.h:1.156
Rev: src/iterators.cmod:1.47
Rev: src/testsuite.in:1.673