Binary to Radix
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Conversions from binary to a power-of-2 radix use a simple and fast
O(N) bit extraction algorithm.
Conversions from binary to other radices use repeated divisions,
first by the biggest power of the radix that fits in a single limb,
then by the radix on the remainders. This is an O(N^2) algorithm and
can be quite time-consuming on large inputs.