[BUGFIX][PATCH 1/1] xenlight_stubs.c: Allow it to build with ocaml 3.09.3

[Don Slutz <dslutz@verizon.com>]

This code was copied from:

http://docs.camlcity.org/docs/godisrc/oasis-ocaml-fd-1.1.1.tar.gz/ocaml-fd-1.1.1/lib/fd_stubs.c

Signed-off-by: Don Slutz <dslutz@verizon.com>
---
 tools/ocaml/libs/xl/xenlight_stubs.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/tools/ocaml/libs/xl/xenlight_stubs.c b/tools/ocaml/libs/xl/xenlight_stubs.c
index 23f253a..8e825ae 100644
--- a/tools/ocaml/libs/xl/xenlight_stubs.c
+++ b/tools/ocaml/libs/xl/xenlight_stubs.c
@@ -35,6 +35,19 @@
 
 #include "caml_xentoollog.h"
 
+/*
+ * Starting with ocaml-3.09.3, CAMLreturn can only be used for ``value''
+ * types. CAMLreturnT was only added in 3.09.4, so we define our own
+ * version here if needed.
+ */
+#ifndef CAMLreturnT
+#define CAMLreturnT(type, result) do { \
+    type caml__temp_result = (result); \
+    caml_local_roots = caml__frame; \
+    return (caml__temp_result); \
+} while (0)
+#endif
+
 /* The following is equal to the CAMLreturn macro, but without the return */
 #define CAMLdone do{ \
 caml_local_roots = caml__frame; \
-- 
1.8.4