Rebase FFmpeg to Negativo17's version'

[korewaChino]

[madonuko]

code in libavdevice/ seems to be invalid

also don't add C specific flags to the cxx macro

[GildedRoach]

code in libavdevice/ seems to be invalid

also don't add C specific flags to the cxx macro

Seems to be.

Also I didn't, you can see where I added them.

%global build_cflags %{__build_flags_lang_c} %{?_distro_extra_cflags} -std=gnu17
%global build_cxxflags %{__build_flags_lang_cxx} %{?_distro_extra_cxxflags} -std=gnu++17