Factorize timercmm.cpp code

Added wxGetCurrentUtime
Put extern declaration in wx/timer.h instead of wx/*/timer.h
Added wxChrono class


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@3754 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/mac/timer.h

@@ -49,16 +49,5 @@ private:
  * But you may need to modify timercmn.cpp.
  */
 
-// Timer functions (milliseconds)
-void WXDLLEXPORT wxStartTimer();
-// Gets time since last wxStartTimer or wxGetElapsedTime
-long WXDLLEXPORT wxGetElapsedTime(bool resetTimer = TRUE);
-
-// EXPERIMENTAL: comment this out if it doesn't compile.
-bool WXDLLEXPORT wxGetLocalTime(long *timeZone, int *dstObserved);
-
-// Get number of seconds since 00:00:00 GMT, Jan 1st 1970.
-long WXDLLEXPORT wxGetCurrentTime();
-
 #endif
     // _WX_TIMER_H_