Adds support for AVX2 for 32-bit types for quicksort and quickselect

[sterrettm2]

This patch adds support for AVX2 for 32-bit data types (int32_t, uint32_t, float) for quicksort and quickselect. It also includes benchmarks and tests for these. Below is a comparison of the performance:

Benchmark                                                                 Time             CPU      Time Old      Time New       CPU Old       CPU New
------------------------------------------------------------------------------------------------------------------------------------------------------
[scalarsort.*random vs. simdsort.*random]_128/uint32_t                 -0.3175         -0.3167          1401           956          1403           959
[scalarsort.*random vs. simdsort.*random]_256/uint32_t                 -0.4046         -0.4039          2044          1217          2045          1219
[scalarsort.*random vs. simdsort.*random]_512/uint32_t                 -0.4359         -0.4336          3625          2045          3626          2054
[scalarsort.*random vs. simdsort.*random]_1k/uint32_t                  -0.7731         -0.7725         15457          3507         15466          3518
[scalarsort.*random vs. simdsort.*random]_5k/uint32_t                  -0.9131         -0.9130        212809         18499        212806         18508
[scalarsort.*random vs. simdsort.*random]_100k/uint32_t                -0.9056         -0.9056       5718828        539986       5718520        539984
[scalarsort.*random vs. simdsort.*random]_1m/uint32_t                  -0.8999         -0.8999      68343297       6840011      68339358       6838741
[scalarsort.*random vs. simdsort.*random]_10m/uint32_t                 -0.8948         -0.8948     793869955      83553573     793781075      83543720
[scalarsort.*random vs. simdsort.*random]_128/int32_t                  -0.3357         -0.3341          1440           957          1442           960
[scalarsort.*random vs. simdsort.*random]_256/int32_t                  -0.4313         -0.4305          2153          1224          2154          1227
[scalarsort.*random vs. simdsort.*random]_512/int32_t                  -0.4535         -0.4524          3793          2073          3794          2078
[scalarsort.*random vs. simdsort.*random]_1k/int32_t                   -0.7714         -0.7712         15606          3568         15623          3575
[scalarsort.*random vs. simdsort.*random]_5k/int32_t                   -0.9138         -0.9138        219140         18888        219138         18897
[scalarsort.*random vs. simdsort.*random]_100k/int32_t                 -0.9063         -0.9063       5858561        549050       5858314        549068
[scalarsort.*random vs. simdsort.*random]_1m/int32_t                   -0.9003         -0.9003      69789096       6959065      69783875       6958046
[scalarsort.*random vs. simdsort.*random]_10m/int32_t                  -0.8949         -0.8949     808208079      84946240     808130032      84933987
[scalarsort.*random vs. simdsort.*random]_128/float                    -0.3752         -0.3741          1565           978          1568           981
[scalarsort.*random vs. simdsort.*random]_256/float                    -0.5006         -0.4985          2502          1250          2503          1255
[scalarsort.*random vs. simdsort.*random]_512/float                    -0.4848         -0.4841          4509          2323          4511          2327
[scalarsort.*random vs. simdsort.*random]_1k/float                     -0.7973         -0.7970         19684          3990         19698          3999
[scalarsort.*random vs. simdsort.*random]_5k/float                     -0.9247         -0.9247        248234         18689        248230         18700
[scalarsort.*random vs. simdsort.*random]_100k/float                   -0.9131         -0.9131       6895883        599356       6895408        599287
[scalarsort.*random vs. simdsort.*random]_1m/float                     -0.9064         -0.9064      81984199       7676841      81976275       7675610
[scalarsort.*random vs. simdsort.*random]_10m/float                    -0.9005         -0.9005     956696234      95182091     956582348      95170689

[r-devulap]

Reviewed only changes in the common qsort file.

[r-devulap]

LGTM. Thank you @sterrettm2!