Add UniformRandomGenerator to Cython, tune Cyth...

Add UniformRandomGenerator to Cython.

Tune Cython by disabling bounds-checking, etc.  However, it did not seem
to make much difference (if any at all).

Before:

    >>> %timeit rand_test.py_rand(out)
    10 loops, best of 3: 22.2 ms per loop
    >>> %timeit rand_test.py_rand_sse(out)
    1000 loops, best of 3: 868 us per loop
    >>> %timeit rand_test.py_rand_sse_cilk(out)
    1000 loops, best of 3: 872 us per loop

After:
    >>> %timeit rand_test.py_uniform_rand(out)
    100 loops, best of 3: 2.96 ms per loop
    >>> %timeit rand_test.py_rand(out)
    10 loops, best of 3: 22.3 ms per loop
    >>> %timeit rand_test.py_rand_sse(out)
    1000 loops, best of 3: 872 us per loop
    >>> %timeit rand_test.py_rand_sse_cilk(out)
    1000 loops, best of 3: 871 us per loop
Prepend "c_" to external C function names
Disable Cython "None"-checks