fix memory leak in deflate stream

Now allow zlib code to free space it had malloc'ed.

Are there user visible changes in this commit?  no

Is bootstrapping needed?   no

Are tests included for new features?  no

Tests run:  manual test watching vm size to verify fix

Change-Id: If988821daf4ffeaee1d58b4f75354ae866d74982

deflate.cl

@@ -329,6 +329,10 @@ actual error:~%  ~a" c)))
 	      then (error "deflateInit2_ returned ~a" err)))
     z-stream))
 
+(defun finish-z-stream (z-stream)
+  ;; free C resources controlled by zlib
+  (deflate-end z-stream))
+
 
 
 (defmethod device-write ((p deflate-stream) buffer start end blocking)
@@ -477,6 +481,11 @@ actual error:~%  ~a" c)))
 	  (finish-zlib-compression p))
 
   (free-deflate-buffer-resource (zlib-static-resources p))
+
+  (let ((z-stream (zlib-z-stream p)))
+    (if* (not (zerop z-stream))
+       then (finish-z-stream  z-stream))
+    (setf (zlib-z-stream p) 0))
 
   (if* (deflate-target-stream p) 
      then (force-output (deflate-target-stream p)))