rework of autofixing system

[florianschanda]

The code formatting has become a bit of a mess, and some specific problems cause a lot of hassle. Plus there are the open issues of fixing not being idempotent, the latest systematic example the matrix indenting.

The system is due a re-write. Specifically:

• token-replay as a general fall-back
• tree-printing for lines that contain single statements without comments; or continued statements with at most one continuation comment