MINOR: buffer: remove bo_ptr()

It was replaced by co_head() when a channel was known, otherwise b_head().
diff --git a/src/raw_sock.c b/src/raw_sock.c
index ad02101..0e1f971 100644
--- a/src/raw_sock.c
+++ b/src/raw_sock.c
@@ -396,7 +396,7 @@
 		if (try < buf->o || flags & CO_SFL_MSG_MORE)
 			send_flag |= MSG_MORE;
 
-		ret = send(conn->handle.fd, bo_ptr(buf), try, send_flag);
+		ret = send(conn->handle.fd, b_head(buf), try, send_flag);
 
 		if (ret > 0) {
 			buf->o -= ret;