implement additive_order for points on an elliptic curve

[was]

This should work:

sage: E = EllipticCurve('11a'); P = E.torsion_subgroup().gens()[0]; P
(5 : 5 : 1)
sage: P.additive_order()
---------------------------------------------------------------------------
NotImplementedError                       Traceback (most recent call last)

/Users/wstein/.sage/temp/resid_tg105.upc.es/5930/_Users_wstein__sage_init_sage_0.py in <module>()

/Users/wstein/build/sage/local/lib/python2.5/site-packages/sage/structure/element.so in sage.structure.element.ModuleElement.additive_order (sage/structure/element.c:8113)()

NotImplementedError: 
sage: P.order()
5

[cremona]

This is a duplicate of #3108 whic hhas a patch waiting review. This ticket can terefore be closed.

[jason]

Please note the request to close this.

[mhansen]

Duplicate of #3108.