Generating fresh names in a source plugin

[Wolfgang Jeltsch]

Hello!

I want to generate AST fragments in a source plugin, and for this I need
to generate fresh (local) names. My current approach is to use
`mkSystemName`, but it, like many of the other name-generating
operations, needs a value of type `Unique`. How can I generate such
values? It seems that the `Hsc` monad doesn’t carry a value of type 
`UniqueSupply` with it.

All the best,
Wolfgang