lavfi: always enable the scale filter and depend on sws.

The scale filter is used for internal colorspace conversions, so it must
always be present.

configure

@@ -1530,11 +1530,11 @@ frei0r_src_filter_deps="frei0r dlopen strtok_r"
 frei0r_src_filter_extralibs='$ldl'
 hqdn3d_filter_deps="gpl"
 ocv_filter_deps="libopencv"
-scale_filter_deps="swscale"
 yadif_filter_deps="gpl"
 
 # libraries
 avdevice_deps="avcodec avformat"
+avfilter_deps="swscale"
 avformat_deps="avcodec"
 
 # programs

libavfilter/Makefile

 NAME = avfilter
-FFLIBS = avutil
+FFLIBS = avutil swscale
 FFLIBS-$(CONFIG_MOVIE_FILTER) += avformat avcodec
-FFLIBS-$(CONFIG_SCALE_FILTER) += swscale
 
 HEADERS = avfilter.h avfiltergraph.h buffersrc.h version.h vsrc_buffer.h
 
@@ -12,6 +11,7 @@ OBJS = allfilters.o                                                     \
        drawutils.o                                                      \
        formats.o                                                        \
        graphparser.o                                                    \
+       vf_scale.o                                                       \
        vsrc_buffer.o
 
 OBJS-$(CONFIG_ANULL_FILTER)                  += af_anull.o
@@ -46,7 +46,6 @@ OBJS-$(CONFIG_OCV_FILTER)                    += vf_libopencv.o
 OBJS-$(CONFIG_OVERLAY_FILTER)                += vf_overlay.o
 OBJS-$(CONFIG_PAD_FILTER)                    += vf_pad.o
 OBJS-$(CONFIG_PIXDESCTEST_FILTER)            += vf_pixdesctest.o
-OBJS-$(CONFIG_SCALE_FILTER)                  += vf_scale.o
 OBJS-$(CONFIG_SELECT_FILTER)                 += vf_select.o
 OBJS-$(CONFIG_SETDAR_FILTER)                 += vf_aspect.o
 OBJS-$(CONFIG_SETPTS_FILTER)                 += vf_setpts.o

libavfilter/allfilters.c

@@ -66,7 +66,6 @@ void avfilter_register_all(void)
     REGISTER_FILTER (OVERLAY,     overlay,     vf);
     REGISTER_FILTER (PAD,         pad,         vf);
     REGISTER_FILTER (PIXDESCTEST, pixdesctest, vf);
-    REGISTER_FILTER (SCALE,       scale,       vf);
     REGISTER_FILTER (SELECT,      select,      vf);
     REGISTER_FILTER (SETDAR,      setdar,      vf);
     REGISTER_FILTER (SETPTS,      setpts,      vf);
@@ -89,9 +88,14 @@ void avfilter_register_all(void)
 
     REGISTER_FILTER (NULLSINK,    nullsink,    vsink);
 
-    /* vsrc_buffer is a part of public API => registered unconditionally */
+    /* those filters are part of public or internal API => registered
+     * unconditionally */
     {
         extern AVFilter avfilter_vsrc_buffer;
         avfilter_register(&avfilter_vsrc_buffer);
     }
+    {
+        extern AVFilter avfilter_vf_scale;
+        avfilter_register(&avfilter_vf_scale);
+    }
 }