Since GLib 2.31 GStaticRecMutex has been deprecated and GRecMutex is used instead. We do not need to initialize GRecMutex since it is static

Fix_Build_against_new_glib.diff

diff --git a/agent/agent.c b/agent/agent.c
index 298a8ec..2adeb30 100644
--- a/agent/agent.c
+++ b/agent/agent.c
@@ -120,7 +120,7 @@ enum
 
 static guint signals[N_SIGNALS];
 
-static GStaticRecMutex agent_mutex = G_STATIC_REC_MUTEX_INIT;    /* Mutex used for thread-safe lib */
+static GRecMutex agent_mutex;    /* Mutex used for thread-safe lib */
 
 static gboolean priv_attach_stream_component (NiceAgent *agent,
     Stream *stream,
@@ -132,12 +132,12 @@ static void priv_free_upnp (NiceAgent *agent);
 
 void agent_lock (void)
 {
-  g_static_rec_mutex_lock (&agent_mutex);
+  g_rec_mutex_lock (&agent_mutex);
 }
 
 void agent_unlock (void)
 {
-  g_static_rec_mutex_unlock (&agent_mutex);
+  g_rec_mutex_unlock (&agent_mutex);
 }