Flush the PutBitsContext at the end of each block when encoding ADPCM IMA QT

Originally committed as revision 24938 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/adpcm.c

@@ -578,6 +578,7 @@ static int adpcm_encode_frame(AVCodecContext *avctx,
             }
         }
 
+        flush_put_bits(&pb);
         dst += put_bits_count(&pb)>>3;
         break;
     }