#109 2014 STANDARD: Implement DYNAMIC LENGTH

[Edward Hart]

See discussion of [feature-requests:#106].

[Simon Sobisch]

Thank you for solving the puzzle "what happened with the dynamic ANY LENGTH items".

I'd really like to see this implemented and it even looks easier than [feature-requests:#60].

I'll add the parser stuff soon, marking it as PENDING but I don't think it takes that much to implement it as long as we only allow it for level 01/77 items. In this case we only need a field attribute "dynamic length" which is evaluated when the field is a non reference-modified receiving item (in this case the new length should be set).
As it's not clearly said in the standard I'd consider a STRING x INTO dynamic-length-item to never to overflow therefore we should produce a warning if the ON OVERLFOW clause is used there.