Array-backed containers: add shrink_to_fit for STL compatibility

Side note: QHash has squeeze(), but there's no shrink_to_fit on
std::unordered_map.

[ChangeLog][QtCore][QByteArray] Added shrink_to_fit().

[ChangeLog][QtCore][QString] Added shrink_to_fit().

[ChangeLog][QtCore][QVarLengthArray] Added shrink_to_fit().

[ChangeLog][QtCore][QVector] Added shrink_to_fit().

Change-Id: Ifd7d28c9bed70727be6308f0191a188201784f61
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

src/corelib/tools/qbytearray.cpp

@@ -1134,6 +1134,13 @@ static inline char qToLower(char c)
     Same as prepend(\a ch).
 */
 
+/*! \fn void QByteArray::shrink_to_fit()
+    \since 5.10
+
+    This function is provided for STL compatibility. It is equivalent to
+    squeeze().
+*/
+
 /*! \fn QByteArray::QByteArray(const QByteArray &other)
 
     Constructs a copy of \a other.

src/corelib/tools/qbytearray.h

@@ -423,6 +423,7 @@ public:
     inline void push_front(char c);
     inline void push_front(const char *c);
     inline void push_front(const QByteArray &a);
+    void shrink_to_fit() { squeeze(); }
 
     static inline QByteArray fromStdString(const std::string &s);
     inline std::string toStdString() const;

src/corelib/tools/qstring.cpp

@@ -8469,6 +8469,15 @@ bool QString::isRightToLeft() const
     Appends the given \a ch character onto the end of this string.
 */
 
+/*! \fn void QString::shrink_to_fit()
+    \since 5.10
+
+    This function is provided for STL compatibility. It is
+    equivalent to squeeze().
+
+    \sa squeeze()
+*/
+
 /*!
     \fn std::string QString::toStdString() const
 

src/corelib/tools/qstring.h

@@ -805,6 +805,7 @@ public:
     inline void push_back(const QString &s) { append(s); }
     inline void push_front(QChar c) { prepend(c); }
     inline void push_front(const QString &s) { prepend(s); }
+    void shrink_to_fit() { squeeze(); }
 
     static inline QString fromStdString(const std::string &s);
     inline std::string toStdString() const;

src/corelib/tools/qvarlengtharray.h

@@ -231,6 +231,7 @@ public:
     inline const T &front() const { return first(); }
     inline T &back() { return last(); }
     inline const T &back() const { return last(); }
+    void shrink_to_fit() { squeeze(); }
 
 private:
     void realloc(int size, int alloc);

src/corelib/tools/qvarlengtharray.qdoc

@@ -190,6 +190,12 @@
     \overload
 */
 
+/*! \fn void QVarLengthArray::shrink_to_fit()
+    \since 5.10
+
+    Same as squeeze(). Provided for STL-compatibility.
+*/
+
 /*! \fn bool QVarLengthArray::isEmpty() const
 
     Returns \c true if the array has size 0; otherwise returns \c false.

src/corelib/tools/qvector.h

@@ -268,6 +268,7 @@ public:
     inline const_reference front() const { return first(); }
     inline reference back() { return last(); }
     inline const_reference back() const { return last(); }
+    void shrink_to_fit() { squeeze(); }
 
     // comfort
     QVector<T> &operator+=(const QVector<T> &l);

src/corelib/tools/qvector.qdoc

@@ -1124,6 +1124,13 @@
     \overload
 */
 
+/*! \fn void QVector::shrink_to_fit()
+    \since 5.10
+
+    This function is provided for STL compatibility. It is equivalent
+    to squeeze().
+*/
+
 /*! \fn bool QVector::empty() const
 
     This function is provided for STL compatibility. It is equivalent