Document that availableMimeTypes can be unreliable.
Document that availableMimeTypes can be unreliable.

Task-number: MOBILITY-2383
Reviewed-by: Ling Hu
Reviewed-by: Jonas Rabbe

enthought/qt-mobility,enthought/qt-mobility,tmcguire/qt-mobility,qtproject/qt-mobility,enthought/qt-mobility,tmcguire/qt-mobility,kaltsi/qt-mobility,kaltsi/qt-mobility,kaltsi/qt-mobility,enthought/qt-mobility,qtproject/qt-mobility,qtproject/qt-mobility,enthought/qt-mobility,qtproject/qt-mobility,kaltsi/qt-mobility,qtproject/qt-mobility,qtproject/qt-mobility,kaltsi/qt-mobility,kaltsi/qt-mobility,tmcguire/qt-mobility,enthought/qt-mobility,tmcguire/qt-mobility,tmcguire/qt-mobility