set-port-position! with overflow value should expand buffer

[Takashi Kato]

For output bytevector port, set-port-position! should forward the location. (expand buffer)

(import (rnrs))
(call-with-bytevector-output-port
 (lambda (out)
   (set-port-position! out 100)
   (put-bytevector out (string->utf8 "hello"))))

[Takashi Kato]

Modified to extend buffer for output bytevector/string if overflow (Fixes #28)

→ <<cset d484790f6736>>