write_queue: Enable updating max_length field

Dequeue and free any excess messages, in case the new queue length
is shorter than the old.

Related: OS#5774
Change-Id: Ibfe51a2faf29f8ae160a9c330c9af0d09b5a9002
diff --git a/src/core/libosmocore.map b/src/core/libosmocore.map
index c0e164b..30814c3 100644
--- a/src/core/libosmocore.map
+++ b/src/core/libosmocore.map
@@ -565,6 +565,7 @@
 osmo_wqueue_clear;
 osmo_wqueue_enqueue;
 osmo_wqueue_enqueue_quiet;
+osmo_wqueue_set_maxlen;
 osmo_wqueue_init;
 rate_ctr_add;
 rate_ctr_difference;