Wrap error-handler around calls to LAUNCH-NEW-INSTANCE and RESUME-URL

in SERVLET-HANDLER.  This will catch most errors, but will fail on
some, e.g. procedure called with wrong number of arguments. As far as
I see, the problem is the underlying error reporting system of
Scsh/Scheme48. Maybe I'm wrong.

scheme/httpd/surflets/packages.scm

@@ -124,6 +124,7 @@
 	sxml-to-html			;SXML->HTML
 	scsh				;regexp et al.
 ;	httpd-file-directory-handlers	;send-file-response
+	handle
 	scheme
 	)
   (files servlet-handler))