keyexch: Group element encodings must have constant length.

keyexch: Group element encodings must have constant length.

SECURITY FIX.  COMPATIBILITY BREAK.

Using the `buf' encodings of group elements leaks length information.
Use the `raw' encoding instead.  I suspect that this really is a bad
security property to have; certainly the security proof for the key
exchange protocol depends on all encodings having the same length.