Revert "Restore memset and fix memmove"

Reverts Jonimoose/libfxcg#25

```
[22:46:47] < gbl08ma> The bad news is, ProgrammerNerd's memmove or something else keeps being broken.
[22:47:03] < gbl08ma> another system error, but this time with a PC of 0x04.
[22:47:36] < gbl08ma> this code works fine with the lazy memmove, and it wasn't written by myself but by a skilled
                      programmer, so I'm sure the problem is with memmove.
```