Replace gcc variadic macro extension with C99 version

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/hw/openpic.c b/hw/openpic.c
index 53747c4..561c609 100644
--- a/hw/openpic.c
+++ b/hw/openpic.c
@@ -40,9 +40,9 @@
 //#define DEBUG_OPENPIC
 
 #ifdef DEBUG_OPENPIC
-#define DPRINTF(fmt, args...) do { printf(fmt , ##args); } while (0)
+#define DPRINTF(fmt, ...) do { printf(fmt , ## __VA_ARGS__); } while (0)
 #else
-#define DPRINTF(fmt, args...) do { } while (0)
+#define DPRINTF(fmt, ...) do { } while (0)
 #endif
 
 #define USE_MPCxxx /* Intel model is broken, for now */