docs: "deprecate" checkchanged and checkconflicts in merge-tool configuration These settings were replaced by check=changed and check=conflicts in a912f26777d3. There is no reason to announce two different ways to achieve the same. The old way should be kept but not announced.

tests: run with PYTHONHASHSEED=random Python set and dict iteration order is in principle undefined but usually 'quite stable'. Setting PYTHONHASHSEED=random will make the iteration order more random in Python 2.6.8 and 2.7.3 and where it has been backported. This can thus help spot dependencies on undefined behaviour and prevent future problems.