BUG/MINOR: mux-h1: Don't return the empty chunk on HEAD responses

HEAD responses must not have any body payload. But, because of a bug, for chunk
reponses, the empty chunk was always added.

This patch fixes the Github issue #146. It must be backported to 2.0 and 1.9.
diff --git a/src/mux_h1.c b/src/mux_h1.c
index e7d769b..37cc825 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -1682,6 +1682,8 @@
 					h1m->flags |= (H1_MF_NO_PHDR|H1_MF_CLEAN_CONN_HDR);
 					h1s->flags &= ~H1S_F_HAVE_O_CONN;
 				}
+				else if ((h1m->flags & H1_MF_RESP) &&  h1s->meth == HTTP_METH_HEAD)
+					h1m->state = H1_MSG_DONE;
 				else
 					h1m->state = H1_MSG_DATA;
 				break;