swscale: rename sws_context_class to ff_sws_context_class

It is an internal swscale symbol and thus should not be exported.
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>

libswscale/options.c

@@ -84,7 +84,7 @@ static const AVOption swscale_options[] = {
     { NULL }
 };
 
-const AVClass sws_context_class = {
+const AVClass ff_sws_context_class = {
     .class_name = "SWScaler",
     .item_name  = sws_context_to_name,
     .option     = swscale_options,
@@ -94,5 +94,5 @@ const AVClass sws_context_class = {
 
 const AVClass *sws_get_class(void)
 {
-    return &sws_context_class;
+    return &ff_sws_context_class;
 }

libswscale/swscale_internal.h

@@ -866,7 +866,7 @@ extern const uint8_t ff_dither_8x8_220[9][8];
 
 extern const int32_t ff_yuv2rgb_coeffs[8][4];
 
-extern const AVClass sws_context_class;
+extern const AVClass ff_sws_context_class;
 
 /**
  * Set c->swscale to an unscaled converter if one exists for the specific

libswscale/utils.c

@@ -1030,7 +1030,7 @@ SwsContext *sws_alloc_context(void)
     av_assert0(offsetof(SwsContext, redDither) + DITHER32_INT == offsetof(SwsContext, dither32));
 
     if (c) {
-        c->av_class = &sws_context_class;
+        c->av_class = &ff_sws_context_class;
         av_opt_set_defaults(c);
     }