Replace gcc variadic macro extension with C99 version

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/linux-user/main.c b/linux-user/main.c
index dc39b05..0d36978 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -1080,12 +1080,12 @@
     return -1;
 }
 
-#define EXCP_DUMP(env, fmt, args...)                                         \
-do {                                                                          \
-    fprintf(stderr, fmt , ##args);                                            \
-    cpu_dump_state(env, stderr, fprintf, 0);                                  \
-    qemu_log(fmt, ##args);                                                   \
-    log_cpu_state(env, 0);                                                      \
+#define EXCP_DUMP(env, fmt, ...)                                        \
+do {                                                                    \
+    fprintf(stderr, fmt , ## __VA_ARGS__);                              \
+    cpu_dump_state(env, stderr, fprintf, 0);                            \
+    qemu_log(fmt, ## __VA_ARGS__);                                      \
+    log_cpu_state(env, 0);                                              \
 } while (0)
 
 void cpu_loop(CPUPPCState *env)