Add default copy and move c'tor/assignment to PresburgerRelation.

mlir/include/mlir/Analysis/Presburger/PresburgerRelation.h

public:
   /// Return a universe set of the specified type that contains all points.
   static PresburgerRelation getUniverse(const PresburgerSpace &space);
 
   /// Return an empty set of the specified type that contains no points.
   static PresburgerRelation getEmpty(const PresburgerSpace &space);
 
   explicit PresburgerRelation(const IntegerRelation &disjunct);
 
+  PresburgerRelation(const PresburgerRelation &) = default;
+  PresburgerRelation(PresburgerRelation &&) = default;
+  PresburgerRelation &operator=(const PresburgerRelation &) = default;
+  PresburgerRelation &operator=(PresburgerRelation &&) = default;
+
   unsigned getNumDomainVars() const { return space.getNumDomainVars(); }
   unsigned getNumRangeVars() const { return space.getNumRangeVars(); }
   unsigned getNumSymbolVars() const { return space.getNumSymbolVars(); }
   unsigned getNumLocalVars() const { return space.getNumLocalVars(); }
   unsigned getNumVars() const { return space.getNumVars(); }
 
   /// Return the number of disjuncts in the union.
   unsigned getNumDisjuncts() const;