Fix signature of fcntl() compatibility dummy

Obviously, this function was never called with two arguments in Windows
code sections, but this will be the case in a subsequent patch.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/mingw.h

@@ -89,7 +89,7 @@ static inline int getuid()
 { return 1; }
 static inline struct passwd *getpwnam(const char *name)
 { return NULL; }
-static inline int fcntl(int fd, int cmd, long arg)
+static inline int fcntl(int fd, int cmd, ...)
 {
 	if (cmd == F_GETFD || cmd == F_SETFD)
 		return 0;