Fix compiler warning, explicitly use 64bit shift

The 1 literal is an int, shifted by an int, and then passed into resize,
which takes a 64 bit value. This makes MSVC complain about

warning C4334: '<<': result of 32-bit shift implicitly converted to 64
bits (was 64-bit shift intended?)

Silence that warning by explicitly making the 1 a 64bit long long.

Change-Id: Ica354166de4adae20e05e176dc72b7ccd1af053f
Reviewed-by: Oliver Eftevaag <oliver.eftevaag@qt.io>
Reviewed-by: Tomi Korpipää <tomi.korpipaa@qt.io>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

src/widgets/graphicsview/qgraphicsscene_bsp.cpp

@@ -103,7 +103,7 @@ void QGraphicsSceneBspTree::initialize(const QRectF &rect, int depth)
     leafCnt = 0;
     nodes.resize((1 << (depth + 1)) - 1);
     nodes.fill(Node());
-    leaves.resize(1 << depth);
+    leaves.resize(1ll << depth);
     leaves.fill(QList<QGraphicsItem *>());
 
     initialize(rect, depth, 0);