Evas: gif decoding bug fix

Gif decoder decodes prior frames sequentially to decode a specific frame.
The last frame of sequential decoding, which is the frame we want to decode,
remains un-decoded until the while loop stops.
The frame count should be incremented after the comparison statement.

src/modules/evas/loaders/gif/evas_image_load_gif.c

@@ -753,9 +753,9 @@ open_file:
                        DGifGetCodeNext(gif, &img);
                     }
                }
-             imgnum++;
              // if we found the image we wanted - get out of here
              if (imgnum >= index) break;
+             imgnum++;
           }
      }
    while (rec != TERMINATE_RECORD_TYPE);