fixed bug in port-position returning 0 for

(port-position 
    (let ([p (open-string-input-port "Hello")]) (read p) p))

scheme/ikarus.io.ss

@@ -1061,6 +1061,8 @@
             (die who "invalid return value from read!" n))
           (unless (<= 0 n (string-length str))
             (die who "return value from read! is out of range" n))
+          (let ([idx ($port-index p)] [pos-vec ($port-position p)])
+            (vector-set! pos-vec 0 (+ idx (vector-ref pos-vec 0))))
           ($set-port-index! p 0) 
           ($set-port-size! p n)
           (cond
@@ -1113,6 +1115,8 @@
             (die who "invalid return value from read!" n))
           (unless (<= 0 n (string-length str))
             (die who "return value from read! is out of range" n))
+          (let ([idx ($port-index p)] [pos-vec ($port-position p)])
+            (vector-set! pos-vec 0 (+ idx (vector-ref pos-vec 0))))
           ($set-port-size! p n)
           (cond
             [(fx= n 0)

scheme/last-revision

@@ -1 +1 @@
-1706
+1707