Update libds.

external/libds

@@ -1 +1 @@
-Subproject commit cd822fedfc1357919b6cba46a9b61e58e2fc1dde
+Subproject commit 1d037dd31e4a242518e2f562d8d2c980443a1869

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.

src/pairmap.c

@@ -1,19 +1,19 @@
 #include "pairmap.h"
 #include <stdlib.h>
 
-unsigned long pairmap_hash_func(void* key){
-  pairmap_key* new_key = key;
+unsigned long pairmap_hash_func(const void* key){
+  const pairmap_key* new_key = key;
   unsigned int hash = 0;
   hash |= ((new_key->x & 0xffff) << 8) + (new_key->y & 0xffff);
   return hash;
 }
-int pairmap_cmp_func(void* a, void* b){
-  pairmap_key* new_key_a = a;
-  pairmap_key* new_key_b = b;
+int pairmap_cmp_func(const void* a, const void* b){
+  const pairmap_key* new_key_a = a;
+  const pairmap_key* new_key_b = b;
   return (new_key_a->x == new_key_b->x) && (new_key_a->y == new_key_b->y);
 }
-void* pairmap_copy_func(void* key){
-  pairmap_key* copy_from = key;
+void* pairmap_copy_func(const void* key){
+  const pairmap_key* copy_from = key;
   pairmap_key* new_key = malloc(sizeof(*new_key));
   if(new_key){
     new_key->x = copy_from->x;