It is the more proper place for them given that this is
the only API using them.
Also use a forward-declaration of AVCodecContext in fdctdsp.h
to avoid including avcodec.h in jfdct(fst|int).c.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
The original code left-shifts negative values, which is undefined
in the C99 specification (the one used during normal Libav compilation).
This change multiplies by (1 << shift), which is functionally equivalent,
but has defined behavior.
With this change, fate-idct8x8 compiled with --fsanitize=undefined works.
Bug-Id: 686
