move QCoreApplication::addLibraryPath call from KApplication to KComponentData

[Maksim Orlovich]

> You can use a mutex to ensure that only one initialisation happens and, if
> any
> other threads enter that code path, they will wait for the initialisation
> to
> finish.
>
> That's what a function-local static does in gcc:
>
> 	static bool initialised = lazyInit();

kdelibs is built with -fno-threadsafe-statics, though; doesn't it disable
this?