do-while with enclosing "not empty" check).
Also do not add additional "not empty" condition for `until` loops when
the given bound is a constant != MIN_VALUE.
Also deleted StepHandler. Since the HeaderInfo.needLastCalculation is
only set to true for handling step progressions, deleted that property
and all associated logic around it.
If the loop end value is a compile-time constant (best we can do now),
and it is safe to iterate over a given range using "naive" for loop
(using '<=' or '>=' in loop condition),
generate such loops for Longs and Chars as well Ints (Bytes, Shorts).
