Major refactoring of the parser.

Major refactoring of the parser.

* Eliminate kludge that makes the parser environment sensitive.
* Eliminate most of the undocumented dynamic parameters.
* Eliminate the ability to change the character sets used in parsing.
* Eliminate never-used parse-objects.
* Don't export parse-object -- it's basically the same as read.
* Convert parser to use define-deferred instead of an explicit initializer.
* Streamline internals somewhat.