new.name: Obtain a name for a new variable that is not already in use
Description
gamm works by transforming a GAMM into something
that can be estimated by lme, but this involves creating new
variables, the names of which should not clash with the names of other
variables on which the model depends. This simple service routine checks a
suggested name against a list of those in use, and if neccesary modifies it
so that there is no clash.