Fix substr tpl func's int type variant issue

Fix substr tpl func's int type variant issue

`substr` template function takes one or two range arguments. Both
arguments must be int type values but if it is used with a calclation
function e.g. `add`, `len` etc, it causes a wrong type error.

This fixes the issue to allow the function to take other integer type
variant like `int64` etc.

This also includes a small fix on no range argument case.

Fix #1190