Refactoring patches

[Yuriy Skalko]

> It is probalby worth retaining the 'const' for passing by value. It'd be meaningless for return values.
> 
> Riki

It is not hard to add `const` again. But here is another important
question -- consistency. If you look on any function in LyX with int or
bool parameter, it will be without `const` and still is not modified
inside the function in 99% cases. I think it is not worth to add it
there and to leave here.

Also I cannot remember the usage of `const` for value parameters in any
common C++ library.


Yuriy