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

server/serial.c

diff --git a/server/serial.c b/server/serial.c
index b2dca50..65dd087 100644
--- a/server/serial.c
+++ b/server/serial.c
@@ -25,6 +25,7 @@
 
 #include <assert.h>
 #include <fcntl.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
@@ -43,6 +44,7 @@
 #endif
 
 #include "winerror.h"
+#include "windef.h"
 #include "winbase.h"
 
 #include "file.h"