Fix most Doxygen warnings. Also add links to stable documentation from unsupported modules (by using the corresponding Doxytags file).

Manually grafted from d107a371c6

unsupported/Eigen/CXX11/src/Tensor/TensorSyclTuple.h

@@ -148,6 +148,8 @@ struct IndexList {};
 template <size_t MIN, size_t N, size_t... Is>
 struct RangeBuilder;
 
+// FIXME Doxygen has problems with recursive inheritance
+#ifndef EIGEN_PARSED_BY_DOXYGEN
 /// \brief base Step: Specialisation of the \ref RangeBuilder when the
 /// MIN==MAX. In this case the Is... is [0 to sizeof...(tuple elements))
 /// \tparam MIN is the starting index of the tuple
@@ -165,6 +167,7 @@ struct RangeBuilder<MIN, MIN, Is...> {
 /// \tparam Is... are the list of generated index so far
 template <size_t MIN, size_t N, size_t... Is>
 struct RangeBuilder : public RangeBuilder<MIN, N - 1, N - 1, Is...> {};
+#endif // EIGEN_PARSED_BY_DOXYGEN
 
 /// \brief IndexRange that returns a [MIN, MAX) index range
 /// \tparam MIN is the starting index in the tuple