Merged r1372 from trunk to fix build problem.

git-svn-id: https://svn.apache.org/repos/asf/serf/branches/0.6.x@1698931 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/outgoing.c b/outgoing.c
index 7e2154c..a7c167b 100644
--- a/outgoing.c
+++ b/outgoing.c
@@ -480,7 +480,7 @@
                             sizeof(struct iovec) * (conn->vec_len - i));
                     conn->vec_len -= i;
                 }
-                ((char *) conn->vec[0].iov_base) += conn->vec[0].iov_len - (len - written);
+                conn->vec[0].iov_base = (char *)conn->vec[0].iov_base + (conn->vec[0].iov_len - (len - written));
                 conn->vec[0].iov_len = len - written;
                 break;
             }