qobject_p.h: Const-correctness fix

Note: This function is being called inside GammaRay

Change-Id: I4260d2b720d87eec829758cf3b86bc0593d964f2
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

src/corelib/kernel/qobject_p.h

@@ -237,7 +237,7 @@ public:
         {
             return reinterpret_cast<const ConnectionList *>(this + 1)[i + 1];
         }
-        int count() { return static_cast<int>(allocated); }
+        int count() const { return static_cast<int>(allocated); }
     };