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

[Yuriy Skalko]

> I don't know enough about this stuff to say much. I think this would be
> worth doing for 2.4.0, as it will probably provide for some speed as well.
> 
> Riki

Committed at 854c9de.

Also I noticed that these files are accessed on every keypress (even on 
navigating document with arrows):

lib/images/undo.svgz
lib/images/textstyle-apply.svgz
lib/images/paste.svgz


Is it *really* necessary?


Yuriy