[plt-scheme] webit for PLT Scheme 4

I've tried using the version of Webit 2.0 on PLaneT; it appears to be
failing only because private/excess.ss is depending on the old version
of the unit library.  If I switch it to use the unit200 compatibility
library, most of the test cases appears to run fine.  Here's the diff:

dyoo at kfisler-ra1:~/work/webit/webit$ diff private/excess.ss~ private/excess.ss
13c13
<            (lib "unit.ss"))
---
>            (lib "unit200.ss"))



The test cases that fail when running tests/tests.ss are:

---
Running test "test list-structure sharing with xml-element-attributes (1)":
(eq?
 (xml-element-attributes `(e (@ . ,yy-attrs) . ,yy-contents))
 yy-attrs)
"Unexpected result: #f\nexpected #t\n"
Running test "test list-structure sharing with xml-element-attributes (2)":
(eq?
 (xml-element-attributes
  `(e (@ (@ (*NAMESPACES* . ,yy-ns-list)) . ,yy-attrs) . ,yy-contents))
 yy-attrs)
"Unexpected result: #f\nexpected #t\n"
Running test "test list-structure sharing with xml-element-ns-list":
(eq?
 (xml-element-ns-list
  `(e (@ (@ (*NAMESPACES* . ,yy-ns-list)) . ,yy-attrs) . ,yy-contents))
 yy-ns-list)
gave the expected result: #t

Running test "test list-structure sharing with xml-element-contents":
(eq?
 (xml-element-contents
  `(e (@ (@ (*NAMESPACES* . ,yy-ns-list)) . ,yy-attrs) . ,yy-contents))
 yy-contents)
"Unexpected result: #f\nexpected #t\n"
---


All of the tests in tests/xml-match-tests.ss appear to run ok.  The
code in the examples needs to be modularized, but other than that,
there doesn't seem to be fundamental difficulty to make things work.

Best of wishes!