MINOR: log: Add log-format variable %HQ, to log HTTP query strings

Since sample fetches are not always available in the response phase,
this patch implements %HQ such that:

  GET /foo?bar=baz HTTP/1.0

...would be logged as:

  ?bar=baz
diff --git a/include/types/log.h b/include/types/log.h
index bbfe020..d0fb966 100644
--- a/include/types/log.h
+++ b/include/types/log.h
@@ -96,6 +96,7 @@
 	LOG_FMT_HTTP_METHOD,
 	LOG_FMT_HTTP_URI,
 	LOG_FMT_HTTP_PATH,
+	LOG_FMT_HTTP_QUERY,
 	LOG_FMT_HTTP_VERSION,
 	LOG_FMT_HOSTNAME,
 	LOG_FMT_UNIQUEID,