doc/ffmpeg: fix metadata language example

Signed-off-by: Lou Logan <lou@lrcd.com>
x86/hecv_res_add: add ff_hevc_transform_add{8,16,32}_8_avx

~15% faster than sse2

Reviewed-by: Mickaël Raulet <mraulet@gmail.com>
Reviewed-by: Christophe Gisquet <christophe.gisquet@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>
avfilter/showwaves: add "cline" mode (centered line)
avfilter/showwaves: split out draw sample code
avfilter/showwaves: add split_channels option
doc/filters: fix cline option name recently added
avfilter/showwaves: align const mode values (cosmetics)