CLEANUP: stconn: tree-wide rename stconn states CS_ST/SB_* to SC_ST/SB_*

This also follows the natural naming. There are roughly 238 changes, all
totally trivial. conn_stream-t.h has become completely void of any
"conn_stream" related stuff now (except its name).
diff --git a/src/dns.c b/src/dns.c
index cf61d17..713008e 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -471,7 +471,7 @@
 	/* if the connection is not established, inform the stream that we want
 	 * to be notified whenever the connection completes.
 	 */
-	if (cs_opposite(cs)->state < CS_ST_EST) {
+	if (cs_opposite(cs)->state < SC_ST_EST) {
 		cs_cant_get(cs);
 		cs_rx_conn_blk(cs);
 		cs_rx_endp_more(cs);
@@ -506,7 +506,7 @@
 	 * the message so that we can take our reference there if we have to
 	 * stop before the end (ret=0).
 	 */
-	if (cs_opposite(cs)->state == CS_ST_EST) {
+	if (cs_opposite(cs)->state == SC_ST_EST) {
 		/* we were already there, adjust the offset to be relative to
 		 * the buffer's head and remove us from the counter.
 		 */