[analyzer] Don't delete TaintConfig copy constructor

[xiaobai]

Summary

Explicitly deleting the copy constructor makes compiling the function
ento::registerGenericTaintChecker difficult with some compilers. When we
construct an llvm::Optional<TaintConfig>, the optional is constructed with a
const TaintConfig reference which it then uses to invoke the deleted TaintConfig
copy constructor.

I've observered this failing with clang 3.8 on Ubuntu 16.04.

[Szelethus]

This really shouldn't matter much. Go for it!

clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp

struct Propagation {
       unsigned VarIndex;
     };
 
     std::vector<Propagation> Propagations;
     std::vector<NameArgsPair> Filters;
     std::vector<NameArgsPair> Sinks;
 
     TaintConfiguration() = default;
-    TaintConfiguration(const TaintConfiguration &) = delete;
+    TaintConfiguration(const TaintConfiguration &) = default;
     TaintConfiguration(TaintConfiguration &&) = default;
-    TaintConfiguration &operator=(const TaintConfiguration &) = delete;
+    TaintConfiguration &operator=(const TaintConfiguration &) = default;
     TaintConfiguration &operator=(TaintConfiguration &&) = default;
   };
 
   /// Convert SignedArgVector to ArgVector.
   ArgVector convertToArgVector(CheckerManager &Mgr, const std::string &Option,
                                SignedArgVector Args);
 
   /// Parse the config.