Implemented the split_sstring function.
Added initialization for split.

This way copy_n_sstring realizes its empty and allocates memory for it.
Forgot to free `locations` in split_sstring().
Changed the return type of split_sstring to a pointer instead of the struct itself.
Removed the strtok equivalents, but left split_sstring() in there.
Fixed code not checking the correct part of array in split_sstring().
Added a check to see if start would be over the length of str in find_str_in_sstring.
Fixed allocation in split_sstring()
Made it more obvious what i is being compared to.
Added documentation for split_sstrings().
Made sure split_sstring() always skips the separator.