avisynth: Fix compilation against current 2.6 header(s).

AviSynth 2.6 (and by extension, AviSynth+) moves these functions
into AVSC_API. This requires both adjusting their normal use,
and for AvxSynth, adjusting the position/use of the USING_AVISYNTH
ifdefs.
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

libavformat/avisynth.c

@@ -74,6 +74,17 @@ typedef struct AviSynthLibrary {
     AVSC_DECLARE_FUNC(avs_release_value);
     AVSC_DECLARE_FUNC(avs_release_video_frame);
     AVSC_DECLARE_FUNC(avs_take_clip);
+#ifdef USING_AVISYNTH
+    AVSC_DECLARE_FUNC(avs_bits_per_pixel);
+    AVSC_DECLARE_FUNC(avs_get_height_p);
+    AVSC_DECLARE_FUNC(avs_get_pitch_p);
+    AVSC_DECLARE_FUNC(avs_get_read_ptr_p);
+    AVSC_DECLARE_FUNC(avs_get_row_size_p);
+    AVSC_DECLARE_FUNC(avs_is_yv24);
+    AVSC_DECLARE_FUNC(avs_is_yv16);
+    AVSC_DECLARE_FUNC(avs_is_yv411);
+    AVSC_DECLARE_FUNC(avs_is_y8);
+#endif
 #undef AVSC_DECLARE_FUNC
 } AviSynthLibrary;
 
@@ -137,6 +148,17 @@ static av_cold int avisynth_load_library(void)
     LOAD_AVS_FUNC(avs_release_value, 0);
     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);
+#endif
 #undef LOAD_AVS_FUNC
 
     atexit(avisynth_atexit_handler);
@@ -460,17 +482,19 @@ static int avisynth_read_packet_video(AVFormatContext *s, AVPacket *pkt,
      * Since AvxSynth doesn't have these functions, special-case
      * it in order to avoid implicit declaration errors. */
 
-    if (avs_is_yv24(avs->vi))
+    if (avs_library.avs_is_yv24(avs->vi))
         bits = 24;
-    else if (avs_is_yv16(avs->vi))
+    else if (avs_library.avs_is_yv16(avs->vi))
         bits = 16;
-    else if (avs_is_yv411(avs->vi))
+    else if (avs_library.avs_is_yv411(avs->vi))
         bits = 12;
-    else if (avs_is_y8(avs->vi))
+    else if (avs_library.avs_is_y8(avs->vi))
         bits = 8;
     else
+        bits = avs_library.avs_bits_per_pixel(avs->vi);
+#else
+    bits = avs_bits_per_pixel(avs->vi);
 #endif
-        bits = avs_bits_per_pixel(avs->vi);
 
     /* Without the cast to int64_t, calculation overflows at about 9k x 9k
      * resolution. */
@@ -499,11 +523,19 @@ static int avisynth_read_packet_video(AVFormatContext *s, AVPacket *pkt,
     dst_p = pkt->data;
     for (i = 0; i < avs->n_planes; i++) {
         plane = avs->planes[i];
+#ifdef USING_AVISYNTH
+        src_p = avs_library.avs_get_read_ptr_p(frame, plane);
+        pitch = avs_library.avs_get_pitch_p(frame, plane);
+
+        rowsize     = avs_library.avs_get_row_size_p(frame, plane);
+        planeheight = avs_library.avs_get_height_p(frame, plane);
+#else
         src_p = avs_get_read_ptr_p(frame, plane);
         pitch = avs_get_pitch_p(frame, plane);
 
         rowsize     = avs_get_row_size_p(frame, plane);
         planeheight = avs_get_height_p(frame, plane);
+#endif
 
         /* Flip RGB video. */
         if (avs_is_rgb24(avs->vi) || avs_is_rgb(avs->vi)) {