Include qhash.h in header instantiating QHash

Include what you use. In this case, the include needs to happen before
qpa/qplatformmenu.h, since that seems to pull in
src/gui/kernel/qwindowdefs.h, which confuses matters (somehow) with a
forward declaration.

Change-Id: Ic09ecb014563e8ebee86f338c7e98e470f82185b
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/plugins/platforms/android/qandroidplatformmenu.h

@@ -40,6 +40,7 @@
 #ifndef QANDROIDPLATFORMMENU_H
 #define QANDROIDPLATFORMMENU_H
 
+#include <qhash.h>
 #include <qpa/qplatformmenu.h>
 #include <qlist.h>
 #include <qmutex.h>