fix some "implicit declaration" warnings in libtrau
diff --git a/openbsc/src/libtrau/rtp_proxy.c b/openbsc/src/libtrau/rtp_proxy.c
index 2aa3a1e..3d34ac6 100644
--- a/openbsc/src/libtrau/rtp_proxy.c
+++ b/openbsc/src/libtrau/rtp_proxy.c
@@ -35,6 +35,7 @@
 #include <openbsc/debug.h>
 #include <openbsc/rtp_proxy.h>
 #include <openbsc/mncc.h>
+#include <openbsc/trau_upqueue.h>
 
 /* attempt to determine byte order */
 #include <sys/param.h>