TrkParametersBase: Fix ambiguities with clang/c++20.

Need to have an exact match for operator== to prevent ambiguities
when compiling with c++20.

Tracking/TrkEvent/TrkParametersBase/TrkParametersBase/ParametersT.h

@@ -128,6 +128,9 @@ public:
   virtual bool operator==(
     const ParametersBase<DIM, T>& rhs) const override final;
 
+  // Needed to avoid ambiguities with c++20.
+  bool operator==(const ParametersT &rhs) const;
+
   /** Virtual clone */
   virtual ParametersT<DIM, T, S>* clone() const override final;
 

Tracking/TrkEvent/TrkParametersBase/TrkParametersBase/ParametersT.icc

@@ -232,6 +232,12 @@ ParametersT<DIM, T, S>::operator==(const ParametersBase<DIM, T>& rhs) const
   // return compatibility of base class parts
   return ParametersBase<DIM, T>::operator==(rhs);
 }
+template<int DIM, class T, class S>
+bool
+ParametersT<DIM, T, S>::operator==(const ParametersT& rhs) const
+{
+  return *this == static_cast<const ParametersBase<DIM, T> &>(rhs);
+}
 /** clone */
 template<int DIM, class T, class S>
 ParametersT<DIM, T, S>*