more doxygenification (issue #5513)

cdr/cdr_csv.c

cdr/cdr_custom.c

cdr/cdr_manager.c

cdr/cdr_odbc.c

cdr/cdr_pgsql.c

cdr/cdr_sqlite.c

cdr/cdr_tds.c

channels/answer.h

channels/chan_sip.c

channels/iax2-parser.c

channels/iax2-parser.h

channels/iax2-provision.c

channels/iax2-provision.h

channels/ring10.h

codecs/adpcm_slin_ex.h

codecs/codec_a_mu.c

codecs/codec_adpcm.c

codecs/codec_alaw.c

codecs/codec_g723_1.c

codecs/codec_g726.c