Fix existing ref counting classes and add new ones.
diff --git a/tools/doxygen/Doxyfile.c++.internal b/tools/doxygen/Doxyfile.c++.internal
index d9184f4..85bbeed 100644
--- a/tools/doxygen/Doxyfile.c++.internal
+++ b/tools/doxygen/Doxyfile.c++.internal
@@ -1038,6 +1038,7 @@
 src/core/lib/support/memory.h \
 src/core/lib/support/mpscq.h \
 src/core/lib/support/murmur_hash.h \
+src/core/lib/support/orphanable.h \
 src/core/lib/support/ref_counted.h \
 src/core/lib/support/ref_counted_ptr.h \
 src/core/lib/support/spinlock.h \