* ecc-internal.h (struct ecc_curve): Delete unused pointer
edwards_root. Update all instances.
* eccdata.c (output_curve): Don't output it.

This makes it possible to share the same code for curve25519 and
curve448 primitives, which use different underlying formulas for
addition and doubling.
Signed-off-by: Daiki Ueno <dueno@redhat.com>

Reorganized curve25519 implementation to take a ratio as input.

Updated and renamed sec_modinv -> ecc_mod_inv, and deleted the
ecc_modp_inv and ecc_modq_inv wrapper functions.

To support curve25519 point operations.