Pass the event timestamp for joystick events

This allows the application to get more fine grained information about controller event timing, and group events that happened together.

src/timer/SDL_timer.c

@@ -538,6 +538,16 @@ void SDL_TicksQuit(void)
     tick_start = 0;
 }
 
+Uint64
+SDL_GetTickStartNS(void)
+{
+    if (!tick_start) {
+        SDL_TicksInit();
+    }
+
+    return (tick_start * SDL_NS_PER_SECOND) / tick_freq;
+}
+
 Uint64
 SDL_GetTicksNS(void)
 {

src/timer/SDL_timer_c.h

@@ -33,6 +33,7 @@ extern void SDL_TicksInit(void);
 extern void SDL_TicksQuit(void);
 extern int SDL_TimerInit(void);
 extern void SDL_TimerQuit(void);
+extern Uint64 SDL_GetTickStartNS(void);
 
 #endif /* SDL_timer_c_h_ */