Setter method on xmpz slices does not modify the value when the slice is unbounded

[vogr]

Setting the value of an unbounded slice of bits on an xmpz object does not seem to have any effect:

In [10]: a = xmpz(0)

In [11]: a[1:] = 0b1111

In [12]: bin(a)
Out[12]: '0b0'

In [13]: a[1:100] = 0b1111

In [14]: bin(a)
Out[14]: '0b11110'