Remove access to all Mozilla-prefixed media queries

In Firefox25, Mozilla added a couple scary media queries (-moz-os-version and -moz-osx-font-smoothing).

I think we should get rid of these, as well as most/all of the prefixed media queries in https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Media_queries#-moz-os-version.

Either just disable them, or make them lie.

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