lavc: change type of AVFrame.channels field from int64_t to int

"channels" is an int in all the other places in the libraries, and the
av_frame_*_channels() accessors return and set an int, so this should not
implicate ABI breaks.
lavfi/abuffersink: add sample_rates field to AVABufferSinkParams

Allow to select sample rates.
lavfi/abuffersink: fix weird indent and spacing
ffplay: set type for channel_layout AudioParams field to int64_t

Reflect the type of the corresponding field in lavc/lavfi.
ffplay: reindent and remove pointless cast in audio_decode_frame() code
ffmpeg: Force a first_pts of 0 for the first configuration of -async use

This is very close to what the default does currently

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
fate: force a first_pts=0 for the aresample test

This is needed to prevent the next commit from breaking fate

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
swr: make the default of nopts for first_pts actually work

Fixes Ticket2210

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
af_biquads: memset(0) cache

Fixes valgrind warnings

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