Add back the elliptic curve (ECC) files

Signed-off-by: Travis Cross <tc@traviscross.com>
Signed-off-by: Philip Zimmermann <prz@mit.edu>
Relicense ECC code under APGLv3 with exception for FreeSWITCH

Thanks to Travis Cross for pushing for this to happen.

Signed-off-by: Philip Zimmermann <prz@mit.edu>
Signed-off-by: Travis Cross <tc@traviscross.com>