Update to the latest Snappy 1.1.2.

Not clear if there are any bugfixes, but there are minor performance
improvements.
Cast away some warnings in Snappy.
Update native with a required new Choice subclass.
Change the MAC address randomiser, proAdhoc server editor, and post processing shader choices to ChoiceWithValueDisplay, so we can see their values.
Merge pull request #6579 from thedax/ui-minor

Tweak the UI a bit.
Merge pull request #6580 from unknownbrackets/snappy-up

Update Snappy to 1.1.2