Forgot to change the number returned when allocation fails in copy_sstring.
Added free() to make sure old memory is freed.
Added a start to s_strncpy.
Removed finished TODO.
Renamed s_strncpy to copy_n_sstring.
Added register to i in copy_n_sstring to speed it up.
Changed the return type of copy_n_sstrings to int.
Removed unnecessary documentation.