ValOrDefDef.name is now TermName

Back then when we planned to introduce type macros, we relaxed the type
of DefDef.name from TermName to Name in order to potentially be able to
accommodate type names for type macros.

Since then, type macros have been cancelled (and, for the record, my
implementation of type macros in paradise 1.0 didn’t involve DefDefs
with TypeNames), and we’ve rolled back the change to DefDef.name.

What we forgot to do, however, was to change the type of ValOrDefDef.name,
which is taken care of in this commit.