Backport checkin:
Replace C++ comment with C comment (fixes SF bug #1593525).
diff --git a/Modules/unicodedata.c b/Modules/unicodedata.c
index a11a0b7..a30d30c 100644
--- a/Modules/unicodedata.c
+++ b/Modules/unicodedata.c
@@ -75,7 +75,7 @@
         {NULL}
 };
 
-// forward declaration
+/* forward declaration */
 static PyTypeObject UCD_Type;
 
 static PyObject*