doc: Fix broken links and incorrect information

ReadOnly was used in places where ReadWrite was the correct value.

Change-Id: I26a2f0de55665ac015fe269e8e5f0d23a2f00e5f
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
(cherry picked from commit 4dcff4ed6d24e6aa061e145bb9de9ff93351a2b1)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit a8fe95f0eab7facc274327a54ca88d4b139eb385)

src/corelib/kernel/qmetaobject.cpp

@@ -460,7 +460,7 @@ QMetaType QMetaObject::metaType() const
 
     The offset is the sum of all the methods in the class's
     superclasses (which is always positive since QObject has the
-    deleteLater() slot and a destroyed() signal).
+    \l{QObject::}{deleteLater()} slot and a \l{QObject::}{destroyed()} signal).
 
     \sa method(), methodCount(), indexOfMethod()
 */
@@ -503,7 +503,7 @@ int QMetaObject::enumeratorOffset() const
 
     The offset is the sum of all the properties in the class's
     superclasses (which is always positive since QObject has the
-    name() property).
+    \l{QObject::}{objectName} property).
 
     \sa property(), propertyCount(), indexOfProperty()
 */

src/corelib/kernel/qobject.cpp

@@ -655,7 +655,7 @@ QMetaCallEvent* QMetaCallEvent::create_impl(QtPrivate::SlotObjUniquePtr slotObj,
     \reentrant
 
     QSignalBlocker can be used wherever you would otherwise use a
-    pair of calls to blockSignals(). It blocks signals in its
+    pair of calls to QObject::blockSignals(). It blocks signals in its
     constructor and in the destructor it resets the state to what
     it was before the constructor ran.
 

src/corelib/kernel/qpermissions.cpp

@@ -577,7 +577,7 @@ QT_PERMISSION_IMPL_COMMON(QContactsPermission)
 {}
 
 /*!
-    Sets whether the request is for read-write (\a mode == AccessMode::ReadOnly) or
+    Sets whether the request is for read-write (\a mode == AccessMode::ReadWrite) or
     read-only (\a mode == AccessMode::ReadOnly) access to the contacts.
 */
 void QContactsPermission::setAccessMode(AccessMode mode)
@@ -634,7 +634,7 @@ QT_PERMISSION_IMPL_COMMON(QCalendarPermission)
 {}
 
 /*!
-    Sets whether the request is for read-write (\a mode == AccessMode::ReadOnly) or
+    Sets whether the request is for read-write (\a mode == AccessMode::ReadWrite) or
     read-only (\a mode == AccessMode::ReadOnly) access to the calendar.
 */
 void QCalendarPermission::setAccessMode(AccessMode mode)