[PATCH] Add move constructor and move assignment operator for FileName class

[Yuriy Skalko]

> Frankly, I am not at ease at all with the way things get updated. I do not understand the Qt mechanisms well enough. If you feel like trying to understand it, please do. Be warn though that we are in a working but fragile situation now, changes will lead to a rough ride but it is probably worth the cost.
> 
> 
> JMarc

Yes, many parts in LyX code are very coupled and some change can cause 
unexpected consequences in seemingly unrelated places (I've already 
encountered this for much smaller changes). So without solid knowledge 
of LyX code it will be hard not to broke anything.

Introducing common testing framework (for both unit and integration 
tests) should help with confidence that things still work after 
introducing the change (but it is not so simple for gui stuff). I think 
this should be the first step before doing such significant 
modifications. Recently I've sent a message on this subject in this 
mailing list but have not received any feedback.


Yuriy