Adds a CELT_GET_LOOKAHEAD() ctl() call instead. Other uses of
celt_mode_info() should not be needed anymore.

Got authorization from all copyright holders

The old constructor is renamed celt_encoder_create_custom(). Same
for the decoder.

Also removes the 8 byte/packet lower bound

by POSIX. The other _t types that are not part of the API are still there
for now. Also, got rid of all that was left of the 64-bit types.

creating the mode. This means that the same mode can be shared for mono and
stereo.

mailing list by Rob Til Freedmen. Also add a bitstream version
check to these applications.

on how to use the API.

bitrate defaults.