* rename 'lenTuple' to 'tupleLen'
Rationale:
`lenTuple` is a tuple consisting of lengths (e.g. `(1, 5, 0)`),
`tupleLen` is a length of a tuple (e.g. `tupleLen((1, 5, 0) == 3`)
* rename 'lenVarargs' to 'varargsLen'
The same rationale as a previous commit. Consistency.