Assembly optimization of strcpy for PowerPC64, using double words instead of bytes to copy strings.
Performance gain with different string size:
| **String size (bytes)** | **size <= 8** | **16 <= size <= 32** | **64 <= size <= 128** | **256 <= size <= 512** | **1024 <= size <= 2048**
| ----- | ----- | ----- | ----- | ----- | -----
| Gain rate | -0,80% | 0,01% | 5,26% | 18,69% | 45,72%
| Gain rate (25/02/19) | 0,11% | 1,8% | 6,66% | 20,37% | 47,15%