Improve performance of copy_set and copy_insert on Erlang

[gertvv]

Applying the same technique of #3 to copy_set and copy_insert yields a meaningful performance gain for small arrays:

Before

Input               Function                       IPS           Min           P99
glearray: 10        set 1k elements         35282.8670        0.0239        0.0443
glearray: 100       set 1k elements         19480.9071        0.0388        0.1017
glearray: 1000      set 1k elements          2682.4007        0.3027        0.6363
glearray: 10k       set 1k elements           260.1347        3.5254        4.6076
glearray: 100k      set 1k elements            15.6756       60.7894       67.5147

After

Input               Function                       IPS           Min           P99
glearray: 10        set 1k elements         45325.3542        0.0185        0.0269
glearray: 100       set 1k elements         22104.3305        0.0361        0.0528
glearray: 1000      set 1k elements          2908.2394        0.3104        0.3869
glearray: 10k       set 1k elements           250.4258        3.6005        4.7467
glearray: 100k      set 1k elements             4.7084      208.5569      222.2722

Performance for the 100k size was really erratic, I have also seen it on par with the "before" result. It just runs too slow to get any meaningful results at all.

[lunagl]

Looks good, could you resolve the conflict so I can merge this?