By "adverbial free relative clause" (maybe there's a better term for this) I mean a relative clause which (a) is headed by an indefinite fused relative pronoun, e.g. English *whoever, whatever*, and (b) has no antecedent in the main clause and thus no close syntactic connection with it (hence "adverbial"). English examples:

a. Whatever the weather is tonight, we'll go out.

b. Whoever wrote that paper, it's silly.

c. Whichever road you take, you'll get to London.

My questions are:

1. Does this construction exist in early Indo-European languages (e.g. Greek, Latin, Sanskrit, Hittite)? If not, how do these languages express such meanings?
2. What syntactic and semantic analyses of such clauses (in any language) have been proposed? They have the unusual property of not having an antecedent and modifying an otherwise syntactically independent sentence, which is odd for relative clauses.