allow running protover test with a testing feature flag

src/rust/protover/Cargo.toml

@@ -3,6 +3,9 @@ authors = ["The Tor Project"]
 version = "0.0.1"
 name = "protover"
 
+[features]
+testing = ["tor_log/testing"]
+
 [dependencies]
 libc = "0.2.22"