Add QStringView::constData()

This is doing the same as data(), but the method is widely being used in
Qt (e.g. in QString), so this will make it easier to change the type of a
variable from QString(Ref) to QStringView in a source compatible way.

Change-Id: Ic49bef688d3ce3c550336edf90130aa5cac8b497
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/text/qstringview.cpp

@@ -359,6 +359,17 @@ QT_BEGIN_NAMESPACE
     \sa begin(), end(), utf16()
 */
 
+/*!
+    \fn const QChar *QStringView::constData() const
+    \since 6.0
+
+    Returns a const pointer to the first character in the string.
+
+    \note The character array represented by the return value is \e not null-terminated.
+
+    \sa data(), begin(), end(), utf16()
+*/
+
 /*!
     \fn const storage_type *QStringView::utf16() const
 

src/corelib/text/qstringview.h

@@ -236,6 +236,7 @@ public:
 
     Q_REQUIRED_RESULT Q_DECL_CONSTEXPR qsizetype size() const noexcept { return m_size; }
     Q_REQUIRED_RESULT const_pointer data() const noexcept { return reinterpret_cast<const_pointer>(m_data); }
+    Q_REQUIRED_RESULT const_pointer constData() const noexcept { return data(); }
     Q_REQUIRED_RESULT Q_DECL_CONSTEXPR const storage_type *utf16() const noexcept { return m_data; }
 
     Q_REQUIRED_RESULT Q_DECL_CONSTEXPR QChar operator[](qsizetype n) const