PERF: series construction perf enhancements, use a fast path based on dt...

[jreback]

This is only 1us improvement, but non-zero
(I measure the existing one at 9us, this puts it at 10, before
this change was about 11)

difference is 3 function calls, so not much more we can do I think
(as this is handling more cases)

-------------------------------------------------------------------------------
Test name                                    | head[ms] | base[ms] |  ratio   |
-------------------------------------------------------------------------------
series_constructor_ndarray                   |   0.0106 |   0.0120 |   0.8874 |
-------------------------------------------------------------------------------
Test name                                    | head[ms] | base[ms] |  ratio   |
-------------------------------------------------------------------------------

Ratio < 1.0 means the target commit is faster then the baseline.
Seed used: 1234

Target [c54848f] : PERF: series construction perf enhancements, use a fast path based on dtype
Base   [9764ea6] : Merge pull request #3332 from jreback/period_perf2