sys/windows: add timeEndPeriod

core/sys/windows/winmm.odin

@@ -6,4 +6,5 @@ foreign import winmm "system:Winmm.lib"
 @(default_calling_convention="stdcall")
 foreign winmm {
 	timeBeginPeriod :: proc(uPeriod: UINT) -> MMRESULT ---
+	timeEndPeriod :: proc(uPeriod: UINT) -> MMRESULT ---
 }