[Development] Starting preparations for Qt 5.1

[Shaw Andy]

> Making of Qt 5.1 minor release will soon start:
> 
> - Plan is to move 'dev' into 'stable' branch on March 19th.
> 
> - After March 19th any changes that are required to get in for 5.1
>   need to be pushed into 'stable' branch. So if your needed changes don't
> make it today,
>   please wait after the merge is done and re-target it.
> 
> - I haven't planed to create any branch yet for commits already in 'stable' and
> not in 'release'. So speak up if this is needed.
> 
> - If we decide to do 5.0.3, it could be done from the 'release' branch.

Considering that people have been developing on stable on the basis that it is in fact 5.0.x, I think we should at least make sure that those changes end up somewhere in case we do a 5.0.3 release for whatever reason. Rather than lose those changes because we merged, could a read only branch be created from the current stable and then merge that into release should a 5.0.3 release happen? So no more work would be done for 5.0.x unless it is decided to make a 5.0.3 release.

Andy