Add complex number support to APIs for returning unique elements #540
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This PR
unique_all,unique_counts,unique_inverse, andunique_values. This PR builds on Add complex number support toequal#528. Namely, by convention, equality is determined by independently comparing real and imaginary components respectively and then performing a logical AND (i.e., ifx = a + bjandy = c + dj, thenx == yiffa == c AND b == d.NaNbe considered unique.equal#528, this PR does not support the one-infinity model (see C99) where complex infinites are treated as equal.