MEDIUM: h1: ensure that 1xx, 204 and 304 don't have a payload body

It's important for the H2 to H1 gateway that the response parser properly
clears the H1 message's body_len when seeing these status codes so that we
don't hang waiting to transfer data that will not come.
diff --git a/src/h1.c b/src/h1.c
index 7e8f19d..856b654 100644
--- a/src/h1.c
+++ b/src/h1.c
@@ -1127,7 +1127,14 @@
 		if (h1m) {
 			long long cl;
 
-			if (isteq(n, ist("transfer-encoding"))) {
+			if (start[st_c] == '1' || /* 100..199 */
+			    isteq(ist2(start + st_c, st_c_l), ist("204")) ||
+			    isteq(ist2(start + st_c, st_c_l), ist("304"))) {
+				/* no contents, claim c-len is present and set to zero */
+				h1m->flags |= H1_MF_CLEN;
+				h1m->curr_len = h1m->body_len = 0;
+			}
+			else if (isteq(n, ist("transfer-encoding"))) {
 				h1m->flags &= ~H1_MF_CLEN;
 				h1m->flags |= H1_MF_CHNK;
 			}