Broken links in documentation in mscgen website

[Fienne]

The mscgen website (https://www.mcternan.me.uk//mscgen/) found in https://github.com/enarx/outreach/issues/36 contains the following broken links:

• https://www.mcternan.me.uk//mscgen/yum/
• http://www.mcternan.me.uk/mscgen/yum/mmcternan.asc
• http://www.stack.nl/~dimitri/doxygen/
• http://www.stack.nl/~dimitri/doxygen/commands.html#cmdmsc
• http://sphinx.pocoo.org/

[Fienne]

@nickvidal I would love to work on this, but I'd also love to have the correct URL to replace the above broken ones with