fsum              405 crypto/curve25519-donna.c   fsum(x, z);
fsum              409 crypto/curve25519-donna.c   fsum(xprime, zprime);
fsum              418 crypto/curve25519-donna.c   fsum(xxprime, zzprime);
fsum              438 crypto/curve25519-donna.c   fsum(zzz, xx);