Maildir-flags synchronization now on master branch

[Kristoffer Ström]

>   1. Don't do maildir-flag things in non-maildir directories
 
>   2. Preserve any unsupported flags when renaming
> 
> Of these, number 1 is likely less important. If someone is very
> concerned about avoiding the maildir-style renaming then they can simply
> configure maildir.synchronize_flags to false.

I'm just pinging that the small feedreader sluk i'm writing/maintaining relies on filenames not changing. 
So if anyone's using it be careful, and #1 would be a tad more important then.

Kristoffer