This way they can be reused by other code without including the whole decoder-specific hevcdec.h Also, add the HEVC_ prefix to them, since similarly named values exist for H.264 as well and are sometimes used in the same code.
This is more consistent with the rest of libav and frees up the hevc.h name for decoder-independent shared declarations.
Signed-off-by: Anton Khirnov <anton@khirnov.net>