Fix MingW build, patch by Kenneth Boyd!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64366 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/System/Win32/Alarm.inc b/lib/System/Win32/Alarm.inc
index 64a2107..dca9e08 100644
--- a/lib/System/Win32/Alarm.inc
+++ b/lib/System/Win32/Alarm.inc
@@ -35,6 +35,9 @@
   return 0;
 }
 
-void Sleep(unsigned n) {
+// Don't pull in all of the Windows headers.
+extern "C" _stdcall void Sleep(unsigned long);
+
+void sys::Sleep(unsigned n) {
   Sleep(n*1000);
 }