convolution in the upcoming AMR-NB floating point decoder. The function scales
and adds a vector, that is lagged by some offset, to another vector with the
same number of elements.

Patch by Colin McQuillan ( m.niloc googlemail com )


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@19634 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b