make code look pretty with matching indentation
don't restrict values of long chars: just parse them, whatever they are
error reporting for token parsing of structure parse trees:

 - if there's any token errors anywhere in a parse tree, whole return value is marked as an error
 - an array of error information is built.  The rationale is to make it
   possible to see the error information without having to traverse the tree
   to find the error-ed tokens
 - in the tree, positions of error-ed tokens are replaced by pointers to
   indices in the array of error information
 - if there's no errors, whole return value is marked as success
note in README