cannot pickle mpi instances #264
Description
Intervals cannot be pickled:
>>> import cPickle
>>> import mpmath
>>> a = mpmath.mpi(10, 30)
>>> cPickle.dumps(a)
PicklingError: Can't pickle <class 'mpmath.ctx_iv.ivmpf'>: it's not the same object as mpmath.ctx_iv.ivmpf
Using current SVN version (> 0.17) and python 2.7
It would be nice to have pickleable intervals for archiving / multiprocessing purposes...
Original issue for #264: http://code.google.com/p/mpmath/issues/detail?id=224
Original author: https://code.google.com/u/112618716509471339233/