Documentation fixes for intrusive: restore the reference documentation and fix

some spelling mistakes.


[SVN r50755]

libs/intrusive

@@ -1 +1 @@
-Subproject commit 119fb288ff69bd0c90bda4bd092a98443f6330fb
+Subproject commit 7517211e4a3b241169f3e6c312e5aedc28ee0954