[C++11] Use 'nullptr'.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210442 91177308-0d34-0410-b5e6-96231b3b80d8
Escape "@function" with \verbatim. [-Wdocumentation]

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210443 91177308-0d34-0410-b5e6-96231b3b80d8