aacdec: allow output reconfiguration on channel changes

Locking the decoder against channel config changes in
parse_adts_frame_header() seems to be unnecessary and
streams with channel config changes are reported.

The sample in http://roundup.libav.org/issue999 still works.
Signed-off-by: Janne Grunau <janne-libav@jannau.net>

libavcodec/aacdec.c

@@ -2079,7 +2079,7 @@ static int parse_adts_frame_header(AACContext *ac, GetBitContext *gb)
 
     size = avpriv_aac_parse_header(gb, &hdr_info);
     if (size > 0) {
-        if (ac->output_configured != OC_LOCKED && hdr_info.chan_config) {
+        if (hdr_info.chan_config) {
             enum ChannelPosition new_che_pos[4][MAX_ELEM_ID];
             memset(new_che_pos, 0, 4 * MAX_ELEM_ID * sizeof(new_che_pos[0][0]));
             ac->m4ac.chan_config = hdr_info.chan_config;