RUN on allegro does not handle stream input

[u-u-h]

On Allegro CL the RUN method does not obtain input from a stream
correctly. Just creating an echo stream does not work, one needs to
copy the data to the provided stream in the :input form of excl.osi:with-command-io.
Test:

(with-input-from-string (s (format nil "Print~%2 lines~%")) 
 (external-program:run "cat" '() :input s :output T :error T))

does not print anything.