Switch to sleep_precise for WaitUntil() which is used for frame timing.

This can improve frame pacing slightly, not just on Windows actually.

Core/FrameTiming.cpp

@@ -19,6 +19,7 @@
 // * Frame skipping. This gets complicated.
 // * The game not actually asking for flips, like in static loading screens
 
+#include "ppsspp_config.h"
 #include "Common/Profiler/Profiler.h"
 #include "Common/Log.h"
 #include "Common/TimeUtil.h"
@@ -35,7 +36,13 @@
 FrameTiming g_frameTiming;
 
 void WaitUntil(double now, double timestamp, const char *reason) {
-#ifdef _WIN32
+#if 1
+	// Use precise timing.
+	sleep_precise(timestamp - now);
+#else
+
+#if PPSSPP_PLATFORM(WINDOWS)
+	// Old method. TODO: Should we make an option?
 	while (time_now_d() < timestamp) {
 		sleep_ms(1, reason); // Sleep for 1ms on this thread
 	}
@@ -45,6 +52,8 @@ void WaitUntil(double now, double timestamp, const char *reason) {
 		usleep((long)(left * 1000000));
 	}
 #endif
+
+#endif
 }
 
 inline Draw::PresentMode GetBestImmediateMode(Draw::PresentMode supportedModes) {