Introduce QDir::listSeparator()

Qt should help abstract such platform differences.
This ifdef is proliferating in user code (seen a few times
in KDE) and even in Qt code (qstandardpaths.cpp).

[ChangeLog][QtCore][QDir] Added listSeparator().

Change-Id: Icad082a51c8efd5d63f7af9bbaedbe4bc15b8937
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qdir.cpp

@@ -1826,6 +1826,8 @@ QFileInfoList QDir::drives()
     underlying operating system. If you want to display paths to the
     user using their operating system's separator use
     toNativeSeparators().
+
+    \sa listSeparator()
 */
 QChar QDir::separator()
 {
@@ -1836,6 +1838,16 @@ QChar QDir::separator()
 #endif
 }
 
+/*!
+    \fn QDir::listSeparator()
+    \since 5.6
+
+    Returns the native path list separator: ':' under Unix
+    and ';' under Windows.
+
+    \sa separator()
+*/
+
 /*!
     Sets the application's current working directory to \a path.
     Returns \c true if the directory was successfully changed; otherwise

src/corelib/io/qdir.h

@@ -177,7 +177,16 @@ public:
 
     static QFileInfoList drives();
 
-    static QChar separator();
+    Q_DECL_CONSTEXPR static inline QChar listSeparator() Q_DECL_NOTHROW
+    {
+#if defined(Q_OS_WIN)
+        return QLatin1Char(';');
+#else
+        return QLatin1Char(':');
+#endif
+    }
+
+    static QChar separator(); // ### Qt6: Make it inline
 
     static bool setCurrent(const QString &path);
     static inline QDir current() { return QDir(currentPath()); }