Update libds.

include/pairmap.h

@@ -36,20 +36,20 @@ typedef struct pairmap_key_s pairmap_key;
  * @param key the key for the hash table.
  * @return the resulting hash.
  */
-unsigned long pairmap_hash_func(void* key);
+unsigned long pairmap_hash_func(const void* key);
 /**
  * Compares two pairmap_key's.
  * @param a the first pairmap_key
  * @param b the second pairmap_key
  * @return
  */
-int pairmap_cmp_func(void* a, void* b);
+int pairmap_cmp_func(const void* a, const void* b);
 /**
  * Copies a pairmap_key.
  * @param key the key to copy.
  * @return the copy of the key.
  */
-void* pairmap_copy_func(void* key);
+void* pairmap_copy_func(const void* key);
 /**
  * Initializes a hash table with functions used for pair maps.
  * @param ht the hash table to initialize.