lavfi: add spp filter.
lavfi/mp: remove mp=spp.

The filter was ported to a native libavfilter filter.
jpeg2000dec: Check compno in get_coc()

Fixes out of array accesses

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>