type conversions fixed to get rid of warnings

sql/ha_heap.cc:
  type conversion fix
sql/opt_range.cc:
  type conversion fix

sql/ha_heap.cc

@@ -175,7 +175,7 @@ void ha_heap::update_key_stats()
       else
       {
         ha_rows hash_buckets= file->s->keydef[i].hash_buckets;
-        uint no_records= hash_buckets ? (uint) file->s->records/hash_buckets : 2;
+        uint no_records= hash_buckets ? (uint) (file->s->records/hash_buckets) : 2;
         if (no_records < 2)
           no_records= 2;
         key->rec_per_key[key->key_parts-1]= no_records;

sql/opt_range.cc

@@ -8376,14 +8376,14 @@ void cost_group_min_max(TABLE* table, KEY *index_info, uint used_key_parts,
   keys_per_block= (table->file->block_size / 2 /
                    (index_info->key_length + table->file->ref_length)
                         + 1);
-  num_blocks= (table_records / keys_per_block) + 1;
+  num_blocks= (uint)(table_records / keys_per_block) + 1;
 
   /* Compute the number of keys in a group. */
   keys_per_group= index_info->rec_per_key[group_key_parts - 1];
   if (keys_per_group == 0) /* If there is no statistics try to guess */
     /* each group contains 10% of all records */
-    keys_per_group= (table_records / 10) + 1;
-  num_groups= (table_records / keys_per_group) + 1;
+    keys_per_group= (uint)(table_records / 10) + 1;
+  num_groups= (uint)(table_records / keys_per_group) + 1;
 
   /* Apply the selectivity of the quick select for group prefixes. */
   if (range_tree && (quick_prefix_records != HA_POS_ERROR))