The documentation for GLib and Gio contains a number of documentation
comment blocks where a parameter reference (e.g. `@err`) is also
discussed in its dereferenced pointer form, which is generally
annotated as `*@err`. This inevitably confuses the MarkDown parser,
which sees the `*` as the beginning of an italicized text span.

To avoid this, replace all `*@foo` with <code>`*foo`</code>, which
loses the `@`-sigil linking it to the `@foo` parameter, but formats
correctly in the rendered documentation. (`@foo` is automatically
formatted like <code>`foo`</code>, so the resulting appearance in
the docs is as intended.)