Fix hang on exit under Windows.

Fix hang on exit under Windows.
TODO: reorganize this code. In particular make sure that this advise from Qt documentation is respected:

Since the QApplication object does so much initialization, it must be created before any other objects related to the user interface are created.

Right now this is not the case. For example, "FontLoader::initFontPath()" is called before the QApplication creation. Moreover, I suspect that a number of global variables contains Qt object that are initialized before the passage through parse_init(). This might also explain the message displayed by Qt that caused the hanging:

QObject::killTimer: timers cannot be stopped from another thread

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@13948 a592a061-630c-0410-9148-cb99ea01b6c8