Included stdlib.h to allow malloc() usage

Depending on indirect inclusion was a mistake and caused compilation to break
on the QNX (BlackBerry NDK 2) target.

Change-Id: I447aec68bfe02447639a096c0c2f928bd4381cd9
Reviewed-by: David Faure <david.faure@kdab.com>

src/corelib/kernel/qmetaobjectbuilder.cpp

@@ -41,6 +41,8 @@
 
 #include "qmetaobjectbuilder_p.h"
 
+#include <stdlib.h>
+
 QT_BEGIN_NAMESPACE
 
 /*!