Append the string body to the end of the string currently
being concatenated as the last string in the string buffer,
and update its count field. If there is no concatenating
string, start one. An error is thrown if there is not
enough room in string space even after a garbage collection.
When there is a concatenating string, S-CAT and
>CAT are the
only basic string operations that can copy a string into the
string buffer. "s-cat"
dstrings ordinary primitive