[RELEASE] Released version 2.3.9

Released version 2.3.9 with the following main changes :
    - BUG/MEDIUM: mux-h1: make h1_shutw_conn() idempotent
    - MEDIUM: backend: use a trylock to grab a connection on high FD counts as well
    - BUG/MINOR: payload: Wait for more data if buffer is empty in payload/payload_lv
    - BUG/MINOR: stats: Apply proper styles in HTML status page.
    - BUG/MEDIUM: time: make sure to always initialize the global tick
diff --git a/VERSION b/VERSION
index bc4abe8..5aa7c52 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.3.8
+2.3.9