While the share of elements used by both is quite big, the amount
of code shared between the decoders and encoders is negligible.
Therefore one can easily split the context if one wants to.
The reasons for doing so are that the non-shared elements
are non-negligible: The stats array which is only used by
the encoder takes 524288B of 868904B (on x64); similarly,
pix_bgr_map which is only used by the decoder takes 16KiB.
Furthermore, using a shared context also entails inclusions
of unneeded headers like put_bits.h for the decoder and get_bits.h
for the encoder (and all of these and much more for huffyuv.c).
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>