guard expressions now re-raise unhandled conditions using

raise-continuable (as per the R6RS errata page, part 7.1)

scheme/last-revision

@@ -1 +1 @@
-1544
+1545

scheme/psyntax.expander.ss

@@ -1328,7 +1328,7 @@
           (syntax-match x* (else)
             [() 
              (let ([g (gensym)])
-               (values `(,g (lambda () (raise ,con))) g))]
+               (values `(,g (lambda () (raise-continuable ,con))) g))]
             [([else e e* ...])
              (values `(begin ,e ,@e*) #f)]
             [(cls . cls*)