MEDIUM: ssl: replace standards DH groups with custom ones

MEDIUM: ssl: replace standards DH groups with custom ones

It is likely that powerful adversaries have been pre-computing the
standardized DH groups, because being widely used have made them
valuable targets. While users are advised to generate their own
DH parameters, replace the ones we ship by values been randomly
generated for this product only.

[wt: replaced dh1024_p, dh2048_p, and dh4096_p with locally-generated
 ones as recommended by Rémi]