C++26 (I hope) is supposed to have this syntax:
```
template for( const auto &element: aggregate )
{
...;
}
```
Thus, I've adjusted this gadget to have a similar name, to enable
simple mechanical code changes. From Alepha, you'd use it
thus:
```
template_for( aggregate ) <=[&]( const auto &element )
{
...;
};
```
