Expose IncludeKind to cxx_gen library
diff --git a/syntax/mod.rs b/syntax/mod.rs
index 2eccdb6..180c40a 100644
--- a/syntax/mod.rs
+++ b/syntax/mod.rs
@@ -52,10 +52,13 @@
     pub end_span: Span,
 }
 
-#[derive(Copy, Clone, PartialEq)]
+/// Whether to emit `#include "path"` or `#include <path>`.
+#[derive(Copy, Clone, PartialEq, Debug)]
 pub enum IncludeKind {
-    Quoted,    // #include "quoted/path/to"
-    Bracketed, // #include <bracketed/path/to>
+    /// `#include "quoted/path/to"`
+    Quoted,
+    /// `#include <bracketed/path/to>`
+    Bracketed,
 }
 
 pub struct ExternType {