Fixed innerHTML assignment for <span> elements

In the both `*span.js` variants, the `innerHTML` of the created `<span>` elements isn't set properly. Instead, an `innerHTML` attribute gets created, which leads to the the placeholder-`<span>` not being visible (as it is empty). It gets visible though after it's been redrawn for the first time (e.g. focused and unfocused once).

I fixed this by explicitly treating the `innerHTML` property.

*Observed with IE11 in IE9 mode.*