for #681, add MeshPacketQueue (a priority queue) to ensure acks get sent quickly

src/mesh/MeshPacketQueue.h

@@ -0,0 +1,33 @@
+#pragma once
+
+#include "MeshTypes.h"
+
+#include <assert.h>
+#include <queue>
+
+// this is an strucure which implements the
+// operator overloading
+struct CompareMeshPacket {
+    bool operator()(MeshPacket *p1, MeshPacket *p2);
+};
+
+/**
+ * A priority queue of packets.
+ *
+ */
+class MeshPacketQueue : public std::priority_queue<MeshPacket *, std::vector<MeshPacket *>, CompareMeshPacket>
+{
+    size_t maxLen;
+  public:
+    MeshPacketQueue(size_t _maxLen);
+
+    /** enqueue a packet, return false if full */
+    bool enqueue(MeshPacket *p);
+
+    // bool isEmpty();
+
+    MeshPacket *dequeue();
+
+    /** Attempt to find and remove a packet from this queue.  Returns true the packet which was removed from the queue */
+    MeshPacket *remove(NodeNum from, PacketId id);
+};