avfilter/af_aphaser: move wave table generation code into separate file

Signed-off-by: Paul B Mahol <onemda@gmail.com>
avfilter: add flanger filter

Signed-off-by: Paul B Mahol <onemda@gmail.com>
avdevice/pulse_audio_dec: clear pa_simple pointer after deallocation

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