doc: Add a few missing const keywords in \fn commands

This adds "const" to a few \fn commands for new operators
in QHash and QMap.

Change-Id: I93cf7aaf88fcb4db17de5810b555b978e8119e20
Task-number: QTBUG-47669
Reviewed-by: Topi Reiniö <[email protected]>

Author: Martin Smith

src/corelib/tools/qhash.cpp

@@ -2240,15 +2240,15 @@ uint qHash(long double key, uint seed) Q_DECL_NOTHROW
     Returns a pointer to the current item's key.
 */
 
-/*! \fn bool QHash::key_iterator::operator==(key_iterator other)
+/*! \fn bool QHash::key_iterator::operator==(key_iterator other) const
 
     Returns \c true if \a other points to the same item as this
     iterator; otherwise returns \c false.
 
     \sa operator!=()
 */
 
-/*! \fn bool QHash::key_iterator::operator!=(key_iterator other)
+/*! \fn bool QHash::key_iterator::operator!=(key_iterator other) const
 
     Returns \c true if \a other points to a different item than this
     iterator; otherwise returns \c false.

src/corelib/tools/qmap.cpp

@@ -1719,15 +1719,15 @@ void QMapDataBase::freeData(QMapDataBase *d)
     Returns a pointer to the current item's key.
 */
 
-/*! \fn bool QMap::key_iterator::operator==(key_iterator other)
+/*! \fn bool QMap::key_iterator::operator==(key_iterator other) const
 
     Returns \c true if \a other points to the same item as this
     iterator; otherwise returns \c false.
 
     \sa operator!=()
 */
 
-/*! \fn bool QMap::key_iterator::operator!=(key_iterator other)
+/*! \fn bool QMap::key_iterator::operator!=(key_iterator other) const
 
     Returns \c true if \a other points to a different item than this
     iterator; otherwise returns \c false.