[analyzer] Small SMT API improvement

[esteffin]

Summary

Removed const qualifier from reset method of SMTSolver and Z3Solver objects.

[NoQ]

Fair enough :)

include/clang/StaticAnalyzer/Core/PathSensitive/SMTSolver.h

   virtual void pop(unsigned NumStates = 1) = 0;
 
   /// Reset the solver and remove all constraints.
-  virtual void reset() const = 0;
+  virtual void reset() = 0;
 
   virtual void print(raw_ostream &OS) const = 0;
 };

lib/StaticAnalyzer/Core/Z3ConstraintManager.cpp

   }
 
   /// Reset the solver and remove all constraints.
-  void reset() const override { Z3_solver_reset(Context.Context, Solver); }
+  void reset() override { Z3_solver_reset(Context.Context, Solver); }
 
   void print(raw_ostream &OS) const override {
     OS << Z3_solver_to_string(Context.Context, Solver);