Clear FF_INPUT_BUFFER_PADDING_SIZE bytes at the end of the temporary buffers used in 4xm decoder.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/4xm.c

@@ -399,6 +399,7 @@ static int decode_p_frame(FourXContext *f, const uint8_t *buf, int length){
     if (!f->bitstream_buffer)
         return AVERROR(ENOMEM);
     f->dsp.bswap_buf(f->bitstream_buffer, (const uint32_t*)(buf + extra), bitstream_size/4);
+    memset((uint8_t*)f->bitstream_buffer + bitstream_size, 0, FF_INPUT_BUFFER_PADDING_SIZE);
     init_get_bits(&f->gb, f->bitstream_buffer, 8*bitstream_size);
 
     f->wordstream= (const uint16_t*)(buf + extra + bitstream_size);
@@ -680,6 +681,7 @@ static int decode_i_frame(FourXContext *f, const uint8_t *buf, int length){
     if (!f->bitstream_buffer)
         return AVERROR(ENOMEM);
     f->dsp.bswap_buf(f->bitstream_buffer, (const uint32_t*)prestream, prestream_size/4);
+    memset((uint8_t*)f->bitstream_buffer + prestream_size, 0, FF_INPUT_BUFFER_PADDING_SIZE);
     init_get_bits(&f->pre_gb, f->bitstream_buffer, 8*prestream_size);
 
     f->last_dc= 0*128*8*8;