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

Martin Storsjö authored Mar 25, 2013 and Niels Möller committed Mar 25, 2013

This avoids unconditionally using clock_gettime in
{ecc,hogweed}-benchmark, falling back to clock() in these
as well.

This makes building succeed on e.g. OS X.