channel_layout.h missing new (non-deprecated)

[SuRGeoNix]

I wanted to access av_channel_layout_from_string and the defines, eg:-

#define AV_CHANNEL_LAYOUT_STEREO            AV_CHANNEL_LAYOUT_MASK(2,  AV_CH_LAYOUT_STEREO)

[Ruslan-B]

Well known issue - I didn't implement clang macro parser to support function like macro, there is a quick fix - just to hard code this as well know function.
However, it seems to be a perfect timing to add support of function like macro.
I'll update on timeline for this.
Meanwhile I'll add temporally hardcoded versions of AV_CHANNEL_LAYOUT_MASK and AV_PIX_FMT_NE.