platform: add ACLAPI to WinSDK

This is needed to implement chmod-like functionality on Windows.  Ensure
that the ACL APIs are available to swift.

Author: compnerd

stdlib/public/Platform/winsdk.modulemap

@@ -18,6 +18,11 @@ module WinSDK [system] [extern_c] {
   }
 
   module core {
+    module acl {
+      header "aclapi.h"
+      export *
+    }
+
     // api-ms-win-core-errhandling-l1-1-0.dll
     module errhandling {
       header "errhandlingapi.h"