Make sure lists are printed with the proper separators as given by the context.

The `Context()->lists` object includes values for the separator to use for each list type.  These were not being honored for TeX output (and some string output). You can check the patch by using

```
Context()->lists->set(List=>{separator=>';'});

$L = List(1,2,3);
$F = Formula("x,1");

BEGIN_TEXT
\(\{$L->TeX\}\) and \(\{$F->TeX\}\)
END_TEXT
```

Without the patch, these should produce comma-separated lists; with the patch, they should be separated by semicolons.
The change is purely cosmetic (the parentheses are not required when the `unless` is used in the reversed form like this).

If you are asking what this routine does, `makeList` is takes the portion of the parse tree that represents a comma separated list and turns it into a flat list.  This is controlled by the `isComma` property of the operator rather than the name of the operator itself.  So it is possible to have commas retain the tree structure rather than flatten the tree, and also possible to have other operators (that are subclasses of this one) to flatten.  That is how semi-colons can be used in place of commas, for example, when commas are used for decimal separators.