swscale: Rename sws_context_class to ff_sws_context_class

It is an internal swscale symbol and thus should not be exported.
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
Signed-off-by: Diego Biurrun <diego@biurrun.de>

libswscale/options.c

@@ -66,9 +66,9 @@ static const AVOption swscale_options[] = {
     { NULL }
 };
 
-const AVClass sws_context_class = { "SWScaler", sws_context_to_name, swscale_options };
+const AVClass ff_sws_context_class = { "SWScaler", sws_context_to_name, swscale_options };
 
 const AVClass *sws_get_class(void)
 {
-    return &sws_context_class;
+    return &ff_sws_context_class;
 }

libswscale/swscale_internal.h

@@ -714,7 +714,7 @@ extern const uint8_t ff_dither_8x8_220[8][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

@@ -867,7 +867,7 @@ SwsContext *sws_alloc_context(void)
     SwsContext *c = av_mallocz(sizeof(SwsContext));
 
     if (c) {
-        c->av_class = &sws_context_class;
+        c->av_class = &ff_sws_context_class;
         av_opt_set_defaults(c);
     }