added chunk_compare() which compares orders chunks

src/libstrongswan/chunk.h

@@ -123,6 +123,12 @@ void chunk_free(chunk_t *chunk);
  */
 chunk_t chunk_skip(chunk_t chunk, size_t bytes);
 
+/**
+ *  Compare two chunks, returns zero if a equals b
+ *  or negative/positive if a is small/greater than b
+ */
+int chunk_compare(chunk_t a, chunk_t b);
+
 /**
  * Compare two chunks for equality,
  * NULL chunks are never equal.