Have inflate() with Z_FINISH avoid the allocation of a window.

inflate() avoided that allocation normally, until it was modified to
update the window on a normal completion so that inflateResetKeep()
could work.  This patch restores that behavior, but only when
Z_FINISH is used successfully to complete an inflation of a stream in
a single call of inflate().  The comments in zlib.h have been updated
accordingly.

inflate.c

@@ -1232,7 +1232,8 @@ int flush;
      */
   inf_leave:
     RESTORE();
-    if (state->wsize || (state->mode < BAD && out != strm->avail_out))
+    if (state->wsize || (out != strm->avail_out && state->mode < BAD &&
+            (state->mode < CHECK || flush != Z_FINISH)))
         if (updatewindow(strm, out)) {
             state->mode = MEM;
             return Z_MEM_ERROR;