Add synonimous for pointers.

m-bitset.h

@@ -39,6 +39,8 @@ typedef struct bitset_s {
   size_t alloc;           // Alloc is the number of allocated limbs
   bitset_limb *ptr;       // Pointer to the allocated limbs
 } bitset_t[1];
+typedef struct bitset_s *bitset_ptr;
+typedef const struct bitset_s bitset_srcptr;
 
 typedef struct bitset_it_s {
   size_t index;           // index to the array of bit