[LyX/master] Reduce the amount of needed boost headers

[Yuriy Skalko]

>> Thanks, Kornel. Signals are also used in generating instant previews, 
>> loading images and converting image formats, monitoring external file 
>> changes. So at first enable generating instant previews, >
> I have it regularly enabled ...
> 
>> then open some 
>> LyX document with many formulas and images in different formats, and 
>> then, during document load,
> 
> You mean 'during creating preview graphics'? I cannot access anything during 
> load
> document.

I've meant when document is opened, but previews are still not ready. 
Another test is closing the document while previews are updating. LyX 
should not crash in this case.

>> try to change some text in this document in 
>> external text editor. This should test signal invocations and connection 
>> handling.
>> 
> 
> For me it seems to work as expected (tried with UserGuide.lyx)

So, is this patch ready to be committed into master to have wider 
testing audience?


Yuriy