QDir::homePath() is not portable

Various standalone portable softwares could have been forced to become portable, if only they hadn't stored their data in a path that involves QDir::homePath().

The problem is that QDir::homePath() checks environment variables such as %HOMEPATH% and %HOME% only after calling GetUserProfileDirectoryW.

Nobody alive seems to know how does GetUserProfileDirectoryW work. But everyone agrees that function beats any attempt to bypass it temporarily. This is unlike environment variables which could be instructed by an external launcher to be modified only inside the session that runs the relevant programs.

Please see http://qt-project.org/forums/viewthread/15481