std::unique_ptr-ify the result of ASTUnit::LoadFromASTFile

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@215320 91177308-0d34-0410-b5e6-96231b3b80d8
unique_ptr-ify CompilerInstance::takeSema

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@215321 91177308-0d34-0410-b5e6-96231b3b80d8
Remove unused CompilerInstance::takeCodeCompletionConsumer

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@215322 91177308-0d34-0410-b5e6-96231b3b80d8