[Concurrency][Windows] Add a couple of includes for Windows.

Actor.cpp does need <io.h> still, and Task.cpp should have been including
<windows.h>

rdar://90776105

Author: al45tair

stdlib/public/Concurrency/Actor.cpp

@@ -19,14 +19,6 @@
 #include <atomic>
 #include <new>
 
-#ifdef _WIN32
-// On Windows, an include below triggers an indirect include of minwindef.h
-// which contains a definition of the `max` macro, generating an error in our
-// use of std::max in this file. This define prevents those macros from being
-// defined.
-#define NOMINMAX
-#endif
-
 #include "../CompatibilityOverride/CompatibilityOverride.h"
 #include "swift/Runtime/Atomic.h"
 #include "swift/Runtime/AccessibleFunction.h"
@@ -68,6 +60,10 @@
 #include <sys/syscall.h>
 #endif
 
+#if defined(_WIN32)
+#include <io.h>
+#endif
+
 #if SWIFT_OBJC_INTEROP
 extern "C" void *objc_autoreleasePoolPush();
 extern "C" void objc_autoreleasePoolPop(void *);

stdlib/public/Concurrency/Task.cpp

@@ -14,6 +14,12 @@
 //
 //===----------------------------------------------------------------------===//
 
+#ifdef _WIN32
+#define WIN32_LEAN_AND_MEAN
+#define NOMINMAX
+#include <windows.h>
+#endif
+
 #include "../CompatibilityOverride/CompatibilityOverride.h"
 #include "swift/Runtime/Concurrency.h"
 #include "swift/ABI/Task.h"