disable redundant image formats, otherwise we wont get any bugreports about -f image2

Originally committed as revision 3683 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffmpeg.c

@@ -2019,7 +2019,7 @@ static void opt_format(const char *arg)
     /* compatibility stuff for pgmyuv */
     if (!strcmp(arg, "pgmyuv")) {
         pgmyuv_compatibility_hack=1;
-        opt_image_format(arg);
+//        opt_image_format(arg);
         arg = "image2";
     }
 

libavformat/allformats.c

@@ -113,17 +113,21 @@ void av_register_all(void)
 
 #ifdef CONFIG_ENCODERS
     /* image formats */
+#if 0
     av_register_image_format(&pnm_image_format);
     av_register_image_format(&pbm_image_format);
     av_register_image_format(&pgm_image_format);
     av_register_image_format(&ppm_image_format);
     av_register_image_format(&pam_image_format);
     av_register_image_format(&pgmyuv_image_format);
+#endif
     av_register_image_format(&yuv_image_format);
+#if 0
 #ifdef CONFIG_ZLIB
     av_register_image_format(&png_image_format);
 #endif
     av_register_image_format(&jpeg_image_format);
+#endif
     av_register_image_format(&gif_image_format);
     av_register_image_format(&sgi_image_format);
 #endif //CONFIG_ENCODERS