v0.1.2 - Vendor the last external dependency

Vendors amfranz/go-xmlrpc-client (the XML-RPC wire-protocol implementation XenAPI's client sits on) into xmlrpc/, dropping the last remaining external module dependency. go.mod now has zero external requires.

Not a reaction to a vulnerability — the library had none, and per its own go.mod no transitive dependencies either. Purely to remove the last external module reference from this fork's supply chain.

No LICENSE file existed upstream at the time of vendoring; attribution to the original author is preserved in xmlrpc/doc.go.

Side effect: go vet now checks the vendored code too (it never did as an external dependency) and flagged two pre-existing minor issues in xmlrpc/request.go and xmlrpc/result.go (unreachable code, a discarded fmt.Errorf() result). Left as-is for this release; candidates for a follow-up cleanup.