MEDIUM: stream-int: replace channel_alloc_buffer() with si_alloc_ibuf() everywhere

Well that's only 3 places (applet.c, stream_interface.c, hlua.c). This
ensures we always clear SI_FL_WAIT_ROOM before setting it on failure,
so that it is granted that SI_FL_WAIT_ROOM always indicates a lack of
room for doing an operation, including the inability to allocate a
buffer for this.
diff --git a/src/applet.c b/src/applet.c
index d7fbb53..6911ab4 100644
--- a/src/applet.c
+++ b/src/applet.c
@@ -36,7 +36,7 @@
 	 * applet in all cases. So this is the applet responsibility to
 	 * check if this buffer was allocated or not. This let a chance
 	 * for applets to do some other processing if needed. */
-	if (!channel_alloc_buffer(si_ic(si), &app->buffer_wait))
+	if (!si_alloc_ibuf(si, &app->buffer_wait))
 		si_applet_cant_put(si);
 
 	/* We always pretend the applet can't get and doesn't want to
diff --git a/src/hlua.c b/src/hlua.c
index 44fb04a..6ad3c82 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -2030,7 +2030,7 @@
 	 * the request buffer if its not required.
 	 */
 	if (s->req.buf.size == 0) {
-		if (!channel_alloc_buffer(&s->req, &appctx->buffer_wait))
+		if (!si_alloc_ibuf(si, &appctx->buffer_wait))
 			goto hlua_socket_write_yield_return;
 	}
 
diff --git a/src/stream_interface.c b/src/stream_interface.c
index e585b1f..8574b4c 100644
--- a/src/stream_interface.c
+++ b/src/stream_interface.c
@@ -1150,10 +1150,8 @@
 	}
 
 	/* now we'll need a input buffer for the stream */
-	if (!channel_alloc_buffer(ic, &(si_strm(si)->buffer_wait))) {
-		si->flags |= SI_FL_WAIT_ROOM;
+	if (!si_alloc_ibuf(si, &(si_strm(si)->buffer_wait)))
 		goto end_recv;
-	}
 
 	/* Important note : if we're called with POLL_IN|POLL_HUP, it means the read polling
 	 * was enabled, which implies that the recv buffer was not full. So we have a guarantee