Generalise Rewriter to work for both fixed and free form code.

[RaoulHC]

At the moment the rewriter is hard coded to split lines according to fixed form, which end at column 72, and use + on column 5 for continuations. This gives incorrect replacements for free form code that are longer than 72 columns, as lines end at column 132 and use an appended & to signify the next line will be a continuation.