Implement native VivoxTest validation (#95)

programs/src/bin/vivox_test.rs

@@ -1,3 +1,3 @@
 fn main() -> std::process::ExitCode {
-    libremetaverse_programs::pending_program("VivoxTest")
+    libremetaverse_programs::vivox_test::main_entry()
 }

programs/src/lib.rs

@@ -8,5 +8,6 @@ pub mod packet_dump;
 pub mod prim_inspector;
 pub mod simple_bot;
 pub mod test_client;
+pub mod vivox_test;
 
 pub use libremetaverse::shim::pending_program;