Implemented ruter_stop_copy().

This function recursively copies a stop_t structure and all its fields, except from its next pointer. A number of support functions was required: wstr_dup() copies a wstr_t structure (required new function wstr_size() which returns the size of a wstr_t and its content in bytes) and ruter_line_copy() which copies a line_t structure in the same manner as ruter_stop_copy.