Activate bugfix 6336 unittest
Various fixes in lockstep and zip

Mainly, they accepted the types R, provided Unqual!R is a range. But that doesn't make sense.

Reduced to only accepting if R itself is a range.

Improved constraints, fixed implementations, removed needles bug workaround.
Merge pull request #1069 from monarchdodra/zipLockstep

Const fixes in Zip and Lockstep