libavformat/avidec: Make unchanged function arguments const

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
libavformat/avienc: Make unchanged function arguments const

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
libavformat/dv: Make unchanged function arguments const

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
libavformat/ffmetadec: Make unchanged function arguments const

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
x86/videodsp: add ff_emu_edge_{hfix,hvar}_avx2

~15% faster than sse2.

Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>