avisynth: Fix detection of AviSynth 2.5

In order to safely exit when the user tries to use AviSynth 2.5, the
continue_on_fail value for 2.6's functions need to be set to 1.
Otherwise, the library loader fails before the 'upgrade to 2.6'
log message appears.
Signed-off-by: Diego Biurrun <diego@biurrun.de>

libavformat/avisynth.c

@@ -140,15 +140,15 @@ static av_cold int avisynth_load_library(void)
     LOAD_AVS_FUNC(avs_release_video_frame, 0);
     LOAD_AVS_FUNC(avs_take_clip, 0);
 #ifdef USING_AVISYNTH
-    LOAD_AVS_FUNC(avs_bits_per_pixel, 0);
-    LOAD_AVS_FUNC(avs_get_height_p, 0);
-    LOAD_AVS_FUNC(avs_get_pitch_p, 0);
-    LOAD_AVS_FUNC(avs_get_read_ptr_p, 0);
-    LOAD_AVS_FUNC(avs_get_row_size_p, 0);
-    LOAD_AVS_FUNC(avs_is_yv24, 0);
-    LOAD_AVS_FUNC(avs_is_yv16, 0);
-    LOAD_AVS_FUNC(avs_is_yv411, 0);
-    LOAD_AVS_FUNC(avs_is_y8, 0);
+    LOAD_AVS_FUNC(avs_bits_per_pixel, 1);
+    LOAD_AVS_FUNC(avs_get_height_p, 1);
+    LOAD_AVS_FUNC(avs_get_pitch_p, 1);
+    LOAD_AVS_FUNC(avs_get_read_ptr_p, 1);
+    LOAD_AVS_FUNC(avs_get_row_size_p, 1);
+    LOAD_AVS_FUNC(avs_is_yv24, 1);
+    LOAD_AVS_FUNC(avs_is_yv16, 1);
+    LOAD_AVS_FUNC(avs_is_yv411, 1);
+    LOAD_AVS_FUNC(avs_is_y8, 1);
 #endif
 #undef LOAD_AVS_FUNC