QHash: add a Qt 7 TODO

The hashing seed's type has been changed from int to size_t in Qt 6.
However the functions setting/getting the seed, and the seed itself,
are still simply int, meaning that we've crippled our seeding.
Add a TODO to amend it.

Change-Id: Ie9dd177149ec299ccf16d4e31f9f4b065804cfed
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/corelib/tools/qhash.cpp

@@ -740,6 +740,7 @@ static uint qt_create_qhash_seed()
 /*
     The QHash seed itself.
 */
+// ### Qt 7: this should use size_t, not int.
 static QBasicAtomicInt qt_qhash_seed = Q_BASIC_ATOMIC_INITIALIZER(-1);
 
 /*!

src/corelib/tools/qhashfunctions.h

@@ -64,6 +64,7 @@ class QByteArray;
 class QString;
 class QLatin1String;
 
+// ### Qt 7: these should use size_t, not int.
 Q_CORE_EXPORT int qGlobalQHashSeed();
 Q_CORE_EXPORT void qSetGlobalQHashSeed(int newSeed);