lavfi: fix FF_API_* definition macros

Fix ABI break occurred after their use.

Bug reported and patch provided by chinsou, fix trac issue #516,
+80cola for me.

libavfilter/avfilter.h

@@ -41,10 +41,10 @@
 #define LIBAVFILTER_BUILD       LIBAVFILTER_VERSION_INT
 
 #ifndef FF_API_OLD_VSINK_API
-#define FF_API_OLD_VSINK_API        (LIBAVUTIL_VERSION_MAJOR < 3)
+#define FF_API_OLD_VSINK_API        (LIBAVFILTER_VERSION_MAJOR < 3)
 #endif
 #ifndef FF_API_OLD_ALL_FORMATS_API
-#define FF_API_OLD_ALL_FORMATS_API (LIBAVUTIL_VERSION_MAJOR < 3)
+#define FF_API_OLD_ALL_FORMATS_API (LIBAVFILTER_VERSION_MAJOR < 3)
 #endif
 
 #include <stddef.h>