Mark internal namespace as \internal

doc/Manual.dox

diff --git a/doc/Manual.dox b/doc/Manual.dox
index d6d4d46..43af857 100644
--- a/doc/Manual.dox
+++ b/doc/Manual.dox
@@ -160,6 +160,6 @@
 /** \addtogroup Splines_Module
     \ingroup Geometry_Reference */
 
-/** \brief Namespace containing low-level routines from the %Eigen library. */
+/** \internal \brief Namespace containing low-level routines from the %Eigen library. */
 namespace internal {}
 }

unsupported/doc/Overview.dox

diff --git a/unsupported/doc/Overview.dox b/unsupported/doc/Overview.dox
index ef361b3..45464a5 100644
--- a/unsupported/doc/Overview.dox
+++ b/unsupported/doc/Overview.dox
@@ -23,6 +23,6 @@
 
 */
 
-/// \brief Namespace containing low-level routines from the %Eigen library.
+/// \internal \brief Namespace containing low-level routines from the %Eigen library.
 namespace internal {}
 }