Add functions to get the amount of bytes in chanenl send and receive buffers.

[meshlink] / src / utcp

diff --git a/src/utcp b/src/utcp
index f1035e971bb894203bdfba6cafbaf0bb30f197eb..cb9223d3b895f1edb35bf7a6fd3aa9305de3f1db 160000 (submodule)
--- a/src/utcp
+++ b/src/utcp
@@ -1 +1 @@
-Subproject commit f1035e971bb894203bdfba6cafbaf0bb30f197eb
+Subproject commit cb9223d3b895f1edb35bf7a6fd3aa9305de3f1db