Changes

Various Unicode fonts are already installed by default on many systems and we should try to support them. However, we should also ensure that supported fonts are ''really'' installed so that users do not wonder why MathML is no working correctly on their system. In former versions of Mozilla, a pop-up dialog appeared and invited the user to go to the [https://developer.mozilla.org/en/Mozilla_MathML_Project/Fonts Fonts] for MathML-enabled Mozilla page. This dialog was really not a pleasant UI and has been removed.  People proposed to add some kind of automated installation {{bug|233950}} {{bug|295193}}. One possible direction could be to use [https://bugzilla.mozilla.org/show_bug.cgi?id=295193#c12 downloadable fonts]. MathJax fonts exit in that format and could be used ({{bug|732830}}).