lavu/hash: Add support for RIPEMD

Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
lavu/adler32: Fix doxy group definition, take two

The description if for the function, not the group.

Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>