Reserve more space for built-in types in id space.

We are running out of type ids for built-in types, 255 is not enough.
QMetaType already contains about ~70 types, situation is maybe not
tragic now, but there is a great chance that we will want to add more
built-in types from different modules like jsondb or declarative. Then
it might be tight, because we are not allowed to reorganize type ids
(it would be a binary incompatible change).

This change was not possible up to now. Old moc generated code assumes
that type id can be safely stored in 8 bits.

This is source compatible change.

Change-Id: Iec600adf6b6196a9f3f06ca6d865911084390cc2
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: João Abecasis <joao.abecasis@nokia.com>
Reviewed-by: Kent Hansen <kent.hansen@nokia.com>

src/corelib/kernel/qmetatype.h

@@ -210,7 +210,7 @@ public:
         QReal = sizeof(qreal) == sizeof(double) ? Double : Float,
 
         UnknownType = 0,
-        User = 256
+        User = 1024
     };
 
     enum TypeFlag {

tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp

@@ -2827,7 +2827,7 @@ Q_DECLARE_METATYPE( MyClass )
 void tst_QVariant::loadUnknownUserType()
 {
     qRegisterMetaType<MyClass>("MyClass");
-    char data[] = {0, 0, 1, 0, 0, 0, 0, 0, 8, 77, 121, 67, 108, 97, 115, 115, 0};
+    char data[] = {0, 0, QMetaType::User >> 8 , char(QMetaType::User), 0, 0, 0, 0, 8, 'M', 'y', 'C', 'l', 'a', 's', 's', 0};
 
     QByteArray ba(data, sizeof(data));
     QDataStream ds(&ba, QIODevice::ReadOnly);