db_flatstore: use unsigned long long for printing time_t value

src/modules/db_flatstore/flat_cmd.c

@@ -142,7 +142,7 @@ int flat_put(db_res_t* res, db_cmd_t* cmd)
 			break;
 
 		case DB_DATETIME:
-			if (fprintf(f, "%u", (unsigned int)cmd->vals[i].v.time) < 0) 
+			if (fprintf(f, "%llu", (unsigned long long)cmd->vals[i].v.time) < 0) 
 				goto error;
 			break;
 

src/modules/db_flatstore/km_flatstore.c

@@ -207,7 +207,7 @@ int flat_db_insert(const db1_con_t* h, const db_key_t* k, const db_val_t* v,
 			break;
 
 		case DB1_DATETIME:
-			fprintf(f, "%u", (unsigned int)VAL_TIME(v + i));
+			fprintf(f, "%llu", (unsigned long long)VAL_TIME(v + i));
 			break;
 
 		case DB1_BLOB: