Optimize sort strings (speedup in 2 - 8 times).

 - For strings length is a multiple of two speedup in 2 - 2.5 times, for multiple of four in 3 - 3.5 times. (Speedup through optimize of comparison of static strings.)
 - Fix bug in conversion between little endian and big endian, for speedup sort strings in 8 times for strings with lengthes: 1/2/4/8 bytes. (Speedup through use optimized for gpu radix_sort for fundamental types).