Doc: Replace some usages of 0/zero/null with \nullptr

Change-Id: Ibe7de11fc6fc41477c35e7d653c6a911855deabb
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

examples/sql/doc/src/drilldown.qdoc

@@ -425,7 +425,7 @@
 
     The \c findWindow() function simply searches through the list of
     existing windows, returning a pointer to the window that matches
-    the given item ID, or 0 if the window doesn't exists.
+    the given item ID, or \nullptr if the window doesn't exists.
 
     Finally, let's take a quick look at our custom \c ImageItem class:
 

src/corelib/kernel/qabstracteventdispatcher.cpp

@@ -160,7 +160,7 @@ QAbstractEventDispatcher::~QAbstractEventDispatcher()
 
 /*!
     Returns a pointer to the event dispatcher object for the specified
-    \a thread. If \a thread is zero, the current thread is used. If no
+    \a thread. If \a thread is \nullptr, the current thread is used. If no
     event dispatcher exists for the specified thread, this function
     returns \nullptr.
 

src/corelib/kernel/qmetaobject.cpp

@@ -599,7 +599,7 @@ static bool methodMatch(const QMetaObject *m, int handle,
 * \internal
 * helper function for indexOf{Method,Slot,Signal}, returns the relative index of the method within
 * the baseObject
-* \a MethodType might be MethodSignal or MethodSlot, or 0 to match everything.
+* \a MethodType might be MethodSignal or MethodSlot, or \nullptr to match everything.
 */
 template<int MethodType>
 static inline int indexOfMethodRelative(const QMetaObject **baseObject,
@@ -731,7 +731,7 @@ int QMetaObject::indexOfSignal(const char *signal) const
     \internal
     Same as QMetaObject::indexOfSignal, but the result is the local offset to the base object.
 
-    \a baseObject will be adjusted to the enclosing QMetaObject, or 0 if the signal is not found
+    \a baseObject will be adjusted to the enclosing QMetaObject, or \nullptr if the signal is not found
 */
 int QMetaObjectPrivate::indexOfSignalRelative(const QMetaObject **baseObject,
                                               const QByteArray &name, int argc,

src/corelib/thread/qmutex.cpp

@@ -487,7 +487,7 @@ QRecursiveMutex::~QRecursiveMutex()
     \fn QMutexLocker::QMutexLocker(QMutex *mutex)
 
     Constructs a QMutexLocker and locks \a mutex. The mutex will be
-    unlocked when the QMutexLocker is destroyed. If \a mutex is zero,
+    unlocked when the QMutexLocker is destroyed. If \a mutex is \nullptr,
     QMutexLocker does nothing.
 
     \sa QMutex::lock()

src/gui/image/qimage.cpp

@@ -3683,8 +3683,8 @@ QImage QImage::fromData(const uchar *data, int size, const char *format)
 /*!
     Saves the image to the file with the given \a fileName, using the
     given image file \a format and \a quality factor. If \a format is
-    0, QImage will attempt to guess the format by looking at \a fileName's
+    \nullptr, QImage will attempt to guess the format by looking at
-    suffix.
+    \a fileName's suffix.
 
     The \a quality factor must be in the range 0 to 100 or -1. Specify
     0 to obtain small compressed files, 100 for large uncompressed
@@ -4099,7 +4099,7 @@ void QImage::setText(const QString &key, const QString &value)
     \l{http://www.libpng.org/pub/png/spec/1.2/png-1.2-pdg.html#C.Anc-text}
     {the PNG specification}. \a s can be any text. \a lang should
     specify the language code (see
-    \l{http://www.rfc-editor.org/rfc/rfc1766.txt}{RFC 1766}) or 0.
+    \l{http://www.rfc-editor.org/rfc/rfc1766.txt}{RFC 1766}) or \nullptr.
     \endomit
 */
 

src/gui/rhi/qrhi.cpp

@@ -2361,7 +2361,7 @@ QRhiResource::Type QRhiRenderPassDescriptor::resourceType() const
 
 /*!
     \return a pointer to a backend-specific QRhiNativeHandles subclass, such as
-    QRhiVulkanRenderPassNativeHandles. The returned value is null when exposing
+    QRhiVulkanRenderPassNativeHandles. The returned value is \nullptr when exposing
     the underlying native resources is not supported by the backend.
 
     \sa QRhiVulkanRenderPassNativeHandles
@@ -4933,7 +4933,7 @@ void QRhiCommandBuffer::dispatch(int x, int y, int z)
 
 /*!
     \return a pointer to a backend-specific QRhiNativeHandles subclass, such as
-    QRhiVulkanCommandBufferNativeHandles. The returned value is null when
+    QRhiVulkanCommandBufferNativeHandles. The returned value is \nullptr when
     exposing the underlying native resources is not supported by, or not
     applicable to, the backend.
 

src/widgets/styles/qproxystyle.cpp

@@ -162,7 +162,7 @@ QStyle *QProxyStyle::baseStyle() const
 
     Ownership of \a style is transferred to QProxyStyle.
 
-    If style is zero, a desktop-dependant style will be
+    If style is \nullptr, a desktop-dependent style will be
     assigned automatically.
 */
 void QProxyStyle::setBaseStyle(QStyle *style)