Add wxTimer::StartOnce().

This is a simple wrapper for wxTimer::Start(timeout, wxTIMER_ONE_SHOT) but is
often more readable and is definitely better than Start(timeout, true) which
many people still use in spite of wxTIMER_ONE_SHOT existence.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74330 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/timer.h

@@ -81,6 +81,10 @@ public:
     // timer if it is already running
     virtual bool Start(int milliseconds = -1, bool oneShot = false);
 
+    // start the timer for one iteration only, this is just a simple wrapper
+    // for Start()
+    bool StartOnce(int milliseconds = -1) { return Start(milliseconds, true); }
+
     // stop the timer, does nothing if the timer is not running
     virtual void Stop();