llc: Convert to C

There's no real reason (other than historical) why code in llc should be
kept as c++ code. Let's rewrite it as C so that it can be included by
existing C code without having to add C->C++ shim, ifdefs all around,
etc.
This simplifies code and easies modification/improvement of the related
objects.

Change-Id: I250680ba581167d7398b2f734769c756cbb61c48
diff --git a/tests/llc/LlcTest.cpp b/tests/llc/LlcTest.cpp
index d98636a..b18f6de 100644
--- a/tests/llc/LlcTest.cpp
+++ b/tests/llc/LlcTest.cpp
@@ -56,7 +56,7 @@
 
 	memcpy(msg_data, data, len);
 
-	queue->enqueue(llc_msg, expire_time);
+	llc_queue_enqueue(queue, llc_msg, expire_time);
 }
 
 static void dequeue_and_check(gprs_llc_queue *queue, const uint8_t *exp_data,
@@ -65,7 +65,7 @@
 	struct msgb *llc_msg;
 	const MetaInfo *info_res;
 
-	llc_msg = queue->dequeue(&info_res);
+	llc_msg = llc_queue_dequeue(queue, &info_res);
 	OSMO_ASSERT(llc_msg != NULL);
 
 	fprintf(stderr, "dequeued msg, length %u (expected %zu), data %s\n",