unique_ptrify the result of CFG::buildCFG/CFGBuilder::buildCFG

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@216755 91177308-0d34-0410-b5e6-96231b3b80d8
unique_ptrify Preprocessor's TokenLexerCache

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@216756 91177308-0d34-0410-b5e6-96231b3b80d8