Make parse errors implement Send and Sync
diff --git a/src/lib.rs b/src/lib.rs
index a534854..b61a2ad 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -569,6 +569,9 @@
 #[cfg(all(any(feature = "full", feature = "derive"), feature = "printing"))]
 mod print;
 
+#[cfg(feature = "parsing")]
+mod thread;
+
 ////////////////////////////////////////////////////////////////////////////////
 
 #[cfg(any(feature = "parsing", feature = "full", feature = "derive"))]