Don't overwrite codec_id with 0 in ff_mp4_read_dec_config_descr().

Fixes ticket #3660.
x86/dsputil: port clear_block functions to yasm

Signed-off-by: James Almer <jamrial@gmail.com>
Reviewed-by: Christophe Gisquet <christophe.gisquet@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
x86/dsputil: port ff_put_signed_pixels_clamped_mmx to yasm

Also add an SSE2 version

Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>