Added stub for SetThreadExecutionState (new function in Win98/2000).

diff --git a/scheduler/thread.c b/scheduler/thread.c
index 6586088..512d6e8 100644
--- a/scheduler/thread.c
+++ b/scheduler/thread.c
@@ -755,6 +755,18 @@
 	return TRUE;
 }
 
+/***********************************************************************
+ * SetThreadExecutionState (KERNEL32.@)
+ *
+ * Informs the system that activity is taking place for
+ * power management purposes.
+ */ 
+EXECUTION_STATE WINAPI SetThreadExecutionState(EXECUTION_STATE flags)
+{
+    FIXME("(%ld): stub\n", flags);
+    return 0;
+}
+
 
 #ifdef __i386__