prefix for all the universe variables.

Check if a term should be elaborated by a fresh variable

Check if a term is universe variable, i.e. its ident should be ?11, ?43...

name_of_uvar t returns the name of universe variable if t is a universe variable, raise Not_uvar otherwise

Internal counter use by this module to generate fresh variables

Generate a fresh name for a universe variable

fresh_uvar env () returns a fresh term representing a universe variable. Add a new declaration into the module env.md