Bug#802671: Tentative patches for version 1.44

[Emmanuel Bourg]

Thank you for the backport Raphael, I started working on the backport
for 1.49 and I've interpreted similarly the changes required. The patch
could be slightly simplified by moving the satisfiesCurveEquation()
functions directly into the two ECPoint subclasses instead of
introducing an intermediary abstract class.

As for testing I face the issue, some help from upstream developers
would be welcome.

Emmanuel Bourg