+The total length of the string data per error is limited to 4096 characters.
+
+ERR_add_error_txt() appends the given text string as additional data to the
+last error queue entry, after inserting the optional separator string if it is
+not NULL and the top error entry does not yet have additional data.
+In case the separator is at the end of the text it is not appended to the data.
+The B<sep> argument may be for instance "\n" to insert a line break when needed.
+If the associated data would become more than 4096 characters long
+(which is the limit given above)
+it is split over sufficiently many new copies of the last error queue entry.
+
+ERR_add_error_mem_bio() is the same as ERR_add_error_txt() except that
+the text string is taken from the given memory BIO.
+It appends '\0' to the BIO contents if not already NUL-terminated.