Based partially on implementation by Michael Niedermayer <michaelni@gmx.at> in
libswresample in FFmpeg. See commits:
7f1ae79d
24ab1abf

Also make this the default value.

Changed to match the number of parameters in conv_func_interleave(), which is
how they are called. The change isn't strictly necessary because the 4th
parameter is not used, but the code is clearer if they match.

Signed-off-by: Justin Ruggles <justin.ruggles@gmail.com>

The current SSE version is slower than the MMX version on Athlon64 and Sandy
Bridge, but the SSE4 and AVX versions are faster on Sandy Bridge.

This would happen at least when lavr is used as a fifo with no
conversion.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
Signed-off-by: Justin Ruggles <justin.ruggles@gmail.com>

This is a new library for audio sample format, channel layout, and sample rate
conversion.