bug in saturation for elliptic curves over Q

[cremona]

Randall Rathbun reports that this crashed badly:

E = EllipticCurve([0,0,0,-13711473216,0])
P = E([-19992,16313472])
Q = E([-24108,-17791704])
R = E([-97104,-20391840])
S = E([-113288,-9969344])
E.saturation([P,Q,R,S])
terminate called after throwing an instance of 'std::bad_alloc'
  what():  std::bad_alloc
---------------------------------------------------------------------------
RuntimeError    

I have diagnosed this as coming from a "shortcoming" in eclib's saturation function when dealing with a non-minimal model. (The curve in the example is non-minimal at 2.)

Of course the best solution is for me to patch eclib (see #10903); but in the meantime the simplest solution is to patch Sage to make sure the eclib's satuation is not called with non-minimal models.

A patch is forthcoming!

[cremona]

applies to 4.6.2.alpha3

[gagansekhon]

All tests passed, Documentation looks good and code also works.