Commented the data structures in queue.h.

- Commented all the data structures in queue, to make it slightly clearer as to their usage and what they store.

src/queue.h

@@ -12,6 +12,7 @@
 // Let the compiler know there will be structs defined elsewhere:
 typedef struct queue queue;
 
+// An enum which is used to state what type of data is being stored in a queueNode:
 typedef enum queueDataType
 {
 	EVENT,
@@ -20,6 +21,7 @@ typedef enum queueDataType
 	OUTPUT_MESSAGE
 } queueDataType;
 
+// A union for storing a pointer to all the types of data a queueNode may hold:
 typedef union queueData
 {
 	outputMessage * outputMessage;
@@ -27,6 +29,7 @@ typedef union queueData
 	commandEvent * command;
 } queueData;
 
+// A queue node, a singly-linked list node for our queue:
 typedef struct queueNode queueNode;
 typedef struct queueNode
 {
@@ -35,6 +38,7 @@ typedef struct queueNode
 	queueNode * next;
 } queueNode;
 
+// A queue, with pointers to the head and tail of the linked list, and data for multi-threading, locking, and an item count.
 typedef struct queue
 {
 	volatile bool lock;