[ruby-core:62862] [RFC] README.EXT: document rb_gc_register_mark_object

Any comment on officially supporting this as part of the C API?

diff --git a/README.EXT b/README.EXT
index d66d6c5..dded850 100644
--- a/README.EXT
+++ b/README.EXT
@@ -1176,6 +1176,12 @@ void rb_global_variable(VALUE *var)
 
   Tells GC to protect these variables.
 
+void rb_gc_register_mark_object(VALUE val)
+
+  Tells GC to protect the object referenced by val.  This requires less
+  memory to track than rb_global_variable, but may only be used if the C
+  variable never changes.
+
 == Constant Definition
 
 void rb_define_const(VALUE klass, const char *name, VALUE val) ::
-- 
Eric Wong