Adding myself as the code owner for the attribute subsystem.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@199151 91177308-0d34-0410-b5e6-96231b3b80d8
LLVM's CMake is now using a feature that wasn't preasant in CMake 2.8.7,
so bump the minimum version in the standalone Clang CMake project as
well.

As I mentioned on the LLVM commit version of this, if this causes any
trouble for folks, just let me know. I'm trying to avoid re-implementing
functionality in CMake, but I will if there are problems using the newer
versions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@199152 91177308-0d34-0410-b5e6-96231b3b80d8