Fix audio resample with audio_index=all.
Fix audio resample with audio_index=all.

This still only works with channels <= 2. Streams with channels > 2 are
resampled downstream with the resample filter. However, that only works
when said stream has the highest sample rate.

zzhhui/mlt,zzhhui/mlt,wideioltd/mlt,mltframework/mlt,ttill/MLT-roto,ttill/MLT-roto,anba8005/mlt,j-b-m/mlt,j-b-m/mlt,siddharudh/mlt,gmarco/mlt-orig,ttill/MLT-roto-tracking,zzhhui/mlt,siddharudh/mlt,siddharudh/mlt,zzhhui/mlt,mltframework/mlt,j-b-m/mlt,mltframework/mlt,siddharudh/mlt,ttill/MLT-roto-tracking,gmarco/mlt-orig,mltframework/mlt,j-b-m/mlt,siddharudh/mlt,ttill/MLT-roto-tracking,ttill/MLT,zzhhui/mlt,anba8005/mlt,anba8005/mlt,ttill/MLT-roto-tracking,ttill/MLT-roto-tracking,xzhavilla/mlt,ttill/MLT,mltframework/mlt,zzhhui/mlt,ttill/MLT,ttill/MLT-roto,wideioltd/mlt,wideioltd/mlt,mltframework/mlt,mltframework/mlt,j-b-m/mlt,ttill/MLT-roto,siddharudh/mlt,ttill/MLT,zzhhui/mlt,mltframework/mlt,j-b-m/mlt,xzhavilla/mlt,ttill/MLT,xzhavilla/mlt,wideioltd/mlt,xzhavilla/mlt,zzhhui/mlt,gmarco/mlt-orig,ttill/MLT,gmarco/mlt-orig,gmarco/mlt-orig,wideioltd/mlt,xzhavilla/mlt,anba8005/mlt,j-b-m/mlt,xzhavilla/mlt,xzhavilla/mlt,ttill/MLT-roto-tracking,anba8005/mlt,wideioltd/mlt,wideioltd/mlt,ttill/MLT-roto,ttill/MLT,siddharudh/mlt,siddharudh/mlt,xzhavilla/mlt,anba8005/mlt,j-b-m/mlt,wideioltd/mlt,mltframework/mlt,ttill/MLT-roto,anba8005/mlt,gmarco/mlt-orig,siddharudh/mlt,gmarco/mlt-orig,xzhavilla/mlt,gmarco/mlt-orig,anba8005/mlt,ttill/MLT-roto,ttill/MLT-roto,zzhhui/mlt,ttill/MLT-roto-tracking,wideioltd/mlt,ttill/MLT-roto-tracking,gmarco/mlt-orig,ttill/MLT,ttill/MLT-roto,j-b-m/mlt,ttill/MLT-roto-tracking,ttill/MLT,j-b-m/mlt,mltframework/mlt,anba8005/mlt