Documentation cleanup for include/clang/AST/DeclCXX.h, no substantive changes.

* Fix up \brief documentation;
* Update C++0x references to C++11;
* Doxygen formatting: bulleted lists start with a single hyphen, not two;
* Fix a typo, "assosiate" -> "associate".


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@185771 91177308-0d34-0410-b5e6-96231b3b80d8