Docs: fix QT_NO_FOREACH/KEYWORDS macro documentation

QT_NO_FOREACH didn't related to anything so the documentation
wasn't generated, and QT_NO_KEYWORDS wasn't documented but
referenced.

Conflict resolution: include relevant documentation that was
added in 3a6c8e02b6d1b0574da52b0087092d0c74aa92c1 as well.

Change-Id: I7b79e61519c186d10f8e8c674705adb3d10bd53a
Reviewed-by: Venugopal Shivashankar <Venugopal.Shivashankar@qt.io>
(cherry picked from commit fd6cfd22831c6ff7078bb97e62439375cfc849f6)
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/corelib/doc/src/foreach-keyword.qdoc

@@ -73,4 +73,18 @@
     \c foreach would not. But using \c foreach always copies the container,
     which is usually not cheap for STL containers. If in doubt, prefer
     \c foreach for Qt containers, and range based \c for for STL ones.
+
+    You can remove the availability of the Qt's \c foreach loop by
+    defining the \c{QT_NO_FOREACH} macro.
+*/
+
+/*!
+    \macro QT_NO_FOREACH
+    \since 6.0
+    \relates <QtGlobal>
+
+    Defining this macro removes the availability of Qt's \c foreach
+    loop.
+
+    \sa QT_NO_KEYWORDS
 */

src/corelib/global/qglobal.cpp

@@ -213,6 +213,19 @@ bool QInternal::activateCallbacks(Callback cb, void **parameters)
     return false;
 }
 
+/*!
+    \macro QT_NO_KEYWORDS
+    \relates <QtGlobal>
+
+    Define this macro to disable the Qt-specific keywords that are usually enabled,
+    such as \c signals and \c slots. Use \c Q_SIGNALS and \c Q_SLOTS instead.
+
+    Libraries should define this macro to make sure that they don't use the generic
+    keywords without the \c Q_ prefix in their public headers.
+
+    \sa QT_NO_FOREACH
+*/
+
 /*!
     \macro QT_NAMESPACE
     \internal