Function histogram

src/api/cpp/histogram.cpp:18–23

namespace af {

array histogram(const array& in, const unsigned nbins, const double minval,
                const double maxval) {
    af_array out = 0;
    AF_THROW(af_histogram(&out, in.get(), nbins, minval, maxval));
    return array(out);
}

array histogram(const array& in, const unsigned nbins) {
    af_array out = 0;