Added SwitchToThread.

dlls/kernel/kernel32.spec

@@ -937,7 +937,7 @@ init	MAIN_KernelInit
 @ stdcall SetWaitableTimer(long ptr long ptr ptr long) SetWaitableTimer
 @ stub SignalObjectAndWait
 @ stub SwitchToFiber
-@ stub SwitchToThread
+@ stdcall SwitchToThread() SwitchToThread
 @ forward TryEnterCriticalSection ntdll.RtlTryEnterCriticalSection
 @ stdcall VirtualAllocEx(long ptr long long long) VirtualAllocEx
 @ stub VirtualFreeEx

dlls/kernel/kernel_main.c

@@ -155,3 +155,9 @@ LONG WINAPI KERNEL_nop(void)
 {
     return 0;
 }
+
+BOOL WINAPI SwitchToThread(VOID)
+{
+    Sleep(0);
+    return 1;
+}