yadif: Fix build with XCode
https://bugzilla.gnome.org/show_bug.cgi?id=710451
diff --git a/gst/yadif/yadif.c b/gst/yadif/yadif.c
index f8b5430..2c92999 100644
--- a/gst/yadif/yadif.c
+++ b/gst/yadif/yadif.c
@@ -32,13 +32,18 @@
#define DECLARE_ALIGNED(n,t,v) t __attribute__ ((aligned (n))) v
#define DECLARE_ASM_CONST(n,t,v) static const t __attribute__((used)) __attribute__ ((aligned (n))) v
+#if defined(__APPLE__)
+# define EXTERN_PREFIX "_"
+#else
+# define EXTERN_PREFIX ""
+#endif
+
#if defined(__PIC__)
# define LOCAL_MANGLE(a) #a "(%%rip)"
#else
# define LOCAL_MANGLE(a) #a
#endif
-#define EXTERN_PREFIX ""
#define MANGLE(a) EXTERN_PREFIX LOCAL_MANGLE(a)
DECLARE_ASM_CONST (16, const xmm_reg, pb_1) = {
