Fixed header dependencies to be fully compatible with the Windows
headers (with help from Dimitrie O. Paun).

diff --git a/dlls/msacm/msacm_main.c b/dlls/msacm/msacm_main.c
index 1d1d017..01bfa75 100644
--- a/dlls/msacm/msacm_main.c
+++ b/dlls/msacm/msacm_main.c
@@ -18,9 +18,13 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
+#include <stdarg.h>
+
+#include "windef.h"
 #include "winbase.h"
 #include "winerror.h"
 #include "mmsystem.h"
+#include "mmreg.h"
 #include "msacm.h"
 #include "msacmdrv.h"
 #include "wineacm.h"