Allow clang tools to display an overview when using the CommonOptionsParser.

Patch by Guillaume Papin.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@186671 91177308-0d34-0410-b5e6-96231b3b80d8
[ASan] Reflect the dropped Mac OS 10.6 support in docs

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@186672 91177308-0d34-0410-b5e6-96231b3b80d8