Simplify and fix ec_GFp_simple_points_make_affine
(which didn't always handle value 0 correctly).

Reviewed-by: emilia@openssl.org
Sync with current 1.0.2 CHANGES file.
Sync with clean-up 1.0.2 CHANGES file.
(If a change is already present in 1.0.1f or 1.0.1h,
don't list it again under changes between 1.0.1h and 1.0.2.)