[docs] Use vim code-block instead of console.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176418 91177308-0d34-0410-b5e6-96231b3b80d8
Default to enabling default-synthesized ivars on all platforms

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176419 91177308-0d34-0410-b5e6-96231b3b80d8