Fix modulo performance (thanks coyotte)


### master

#### GCC

$ python -m timeit -c "from pi_buffon import pi_estimate; pi_estimate(2200000,[x/1000. for x in range(1000)],1000) "
10 loops, best of 3: 87.3 msec per loop

$ python -m timeit -c "from prime_decomposition import fac, test_decompose; fac(2**59 - 1)"
100 loops, best of 3: 14 msec per loop

$ python -m timeit -c "from prime_decomposition import fac, test_decompose; test_decompose(2**59 - 1)"
git checkout modulo10 loops, best of 3: 509 msec per loop

#### Clang

$ python -m timeit -c "from pi_buffon import pi_estimate; pi_estimate(2200000,[x/1000. for x in range(1000)],1000) "
10 loops, best of 3: 81.3 msec per loop

## This PR

#### GCC

$ python -m timeit -c "from pi_buffon import pi_estimate; pi_estimate(2200000,[x/1000. for x in range(1000)],1000) "
10 loops, best of 3: 44.7 msec per loop

$ python -m timeit -c "from prime_decomposition import fac, test_decompose; fac(2**59 - 1)"
100 loops, best of 3: 9.21 msec per loop

$ python -m timeit -c "from prime_decomposition import fac, test_decompose; test_decompose(2**59 - 1)"
10 loops, best of 3: 287 msec per loop

#### Clang

$ python -m timeit -c "from pi_buffon import pi_estimate; pi_estimate(2200000,[x/1000. for x in range(1000)],1000) "
10 loops, best of 3: 45 msec per loop

### Before changes in master c04330eb17e0f57d605dd1048e5c959bea1b02e7

#### GCC

$ python -m timeit -c "from pi_buffon import pi_estimate; pi_estimate(2200000,[x/1000. for x in range(1000)],1000) "
10 loops, best of 3: 45 msec per loop

$ python -m timeit -c "from prime_decomposition import fac, test_decompose; fac(2**59 - 1)"
100 loops, best of 3: 9.03 msec per loop

$ python -m timeit -c "from prime_decomposition import fac, test_decompose; test_decompose(2**59 - 1)"
10 loops, best of 3: 279 msec per loop


#### Clang

$ python -m timeit -c "from pi_buffon import pi_estimate; pi_estimate(2200000,[x/1000. for x in range(1000)],1000) "
10 loops, best of 3: 42.6 msec per loop