Fix bug with wxStopWatch::Start() not resuming paused stopwatch any more.

Since r69835 the stop watch remained paused even when Start() was called. Do
resume it when restarting it both for backwards compatibility and because it
makes more sense and also document this behaviour.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@69921 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/stopwatch.h

@@ -61,6 +61,10 @@ public:
 
     /**
         (Re)starts the stop watch with a given initial value.
+
+        The stopwatch will always be running after calling Start(), even if
+        Pause() had been called before and even if it had been called multiple
+        times.
     */
     void Start(long milliseconds = 0);