Make the maximum size of the jbuf at least 4 times the capacity.

Should prevent issues that might occur because a different thread is
reading it.

toxav/codec.c

@@ -133,7 +133,7 @@ static JitterBuffer *jbuf_new(uint32_t capacity)
 {
     unsigned int size = 1;
 
-    while (size <= capacity) {
+    while (size <= (capacity * 4)) {
         size *= 2;
     }