QScoped(Array)Pointer: canonicalize swapping

This includes:
- have nothrow member-swap
- have ADL non-member swap
- not specialize qSwap or std::swap

Also prevent QScopedPointer <-> QScopedArrayPointer swaps by overloading
swap (both member and non-member) on QScopedArrayPointer. It's not 100%
safe, but it's what we're doing elsewhere (QMulti(Map,Hash), say).

That's technically a SiC change if users expected (qualified) std::swap
to invoke QScopedPointer::swap(), but those users were doing it wrong to
begin with, and they now get a compile-error instead of silent pessimization,
because generic std::swap() doesn't work on QScopedPointer, due to lack
of copy (and thus move) semantics.

Change-Id: I3ab5c1668722a2c8ccafc16f57310ce8d4bffbd6
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

src/corelib/tools/qscopedpointer.h

@@ -162,7 +162,7 @@ public:
         return oldD;
     }
 
-    inline void swap(QScopedPointer<T, Cleanup> &other)
+    void swap(QScopedPointer<T, Cleanup> &other) Q_DECL_NOTHROW
     {
         qSwap(d, other.d);
     }
@@ -189,18 +189,9 @@ inline bool operator!=(const QScopedPointer<T, Cleanup> &lhs, const QScopedPoint
 }
 
 template <class T, class Cleanup>
-Q_INLINE_TEMPLATE void qSwap(QScopedPointer<T, Cleanup> &p1, QScopedPointer<T, Cleanup> &p2)
+inline void swap(QScopedPointer<T, Cleanup> &p1, QScopedPointer<T, Cleanup> &p2) Q_DECL_NOTHROW
 { p1.swap(p2); }
 
-QT_END_NAMESPACE
-namespace std {
-    template <class T, class Cleanup>
-    Q_INLINE_TEMPLATE void swap(QT_PREPEND_NAMESPACE(QScopedPointer)<T, Cleanup> &p1, QT_PREPEND_NAMESPACE(QScopedPointer)<T, Cleanup> &p2)
-    { p1.swap(p2); }
-}
-QT_BEGIN_NAMESPACE
-
-
 
 namespace QtPrivate {
     template <typename X, typename Y> struct QScopedArrayEnsureSameType;
@@ -230,6 +221,9 @@ public:
         return this->d[i];
     }
 
+    void swap(QScopedArrayPointer &other) Q_DECL_NOTHROW // prevent QScopedPointer <->QScopedArrayPointer swaps
+    { QScopedPointer<T, Cleanup>::swap(other); }
+
 private:
     explicit inline QScopedArrayPointer(void *) {
         // Enforce the same type.
@@ -245,6 +239,10 @@ private:
     Q_DISABLE_COPY(QScopedArrayPointer)
 };
 
+template <typename T, typename Cleanup>
+inline void swap(QScopedArrayPointer<T, Cleanup> &lhs, QScopedArrayPointer<T, Cleanup> &rhs) Q_DECL_NOTHROW
+{ lhs.swap(rhs); }
+
 QT_END_NAMESPACE
 
 #endif // QSCOPEDPOINTER_H