- fixed `QabElem` for GAP cyclotomics:
  We have to use the cyclotomic fields that are cached in `abelian_closure(QQ)`,  otherwise the elements created by `QabElem` will not be compatible.

- fixed the printing of cyclotomics in Julia:
  The correct cyclotomic fields cause a different `string` format for elements.

- In `show` for character tables, if the irrational values are shown via
  symbolic names then use `*` to denote algebraic conjugacy in quadratic fields
  (relative names like `X` and `X*`).

- Use `"text/latex"` not `"text/html"` to specify that one wants LaTeX format.