unique_ptrify BugReporter::visitors

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@217205 91177308-0d34-0410-b5e6-96231b3b80d8
unique_ptrify the result of ConstraintManagerCreator and StoreManagerCreator

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@217206 91177308-0d34-0410-b5e6-96231b3b80d8