Imports of package secretbox

PathSynopsis
golang.org/x/crypto/internal/aliasPackage alias implements memory aliasing tests.
golang.org/x/crypto/internal/poly1305Package poly1305 implements Poly1305 one-time message authentication code as specified in https://cr.yp.to/mac/poly1305-20050329.pdf.
golang.org/x/crypto/salsa20/salsaPackage salsa provides low-level access to functions in the Salsa family.