WinSDK: extract Multimedia submodule

Some of the headers in the Multimedia subsystem were not included in any other submodule of WinSDK. This change adds them to WinSDK.

Author: egorzhdan

stdlib/public/Platform/winsdk.modulemap

@@ -197,6 +197,30 @@ module WinSDK [system] {
     }
   }
 
+  module Multimedia {
+    module DigitalVideo {
+      header "Digitalv.h"
+      export *
+    }
+
+    module Video {
+      header "Vfw.h"
+      export *
+
+      link "Vfw32.Lib"
+    }
+
+    header "mmeapi.h"
+    header "mmddk.h"
+    header "mmsystem.h"
+    header "mmiscapi.h"
+    header "timeapi.h"
+    header "joystickapi.h"
+    export *
+
+    link "WinMM.Lib"
+  }
+
   module Shell {
     header "ShlObj.h"
     export *