Add Venafi Gen2 log

It's not qualified by Chrome yet, but it is accumulating so many entries
already that I think it's good to get a head start on monitoring it.

logs.go

@@ -104,6 +104,11 @@ var DefaultLogs = []LogInfo{
 		Url: "www.certificatetransparency.cn/ct",
 		MMD: 86400,
 	},
+	{
+		Key: mustDecodeBase64("MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEjicnerZVCXTrbEuUhGW85BXx6lrYfA43zro/bAna5ymW00VQb94etBzSg4j/KS/Oqf/fNN51D8DMGA2ULvw3AQ=="),
+		Url: "ctlog-gen2.api.venafi.com",
+		MMD: 86400,
+	},
 }
 
 // Logs which monitor certs from distrusted roots