[Doc] Revert Doxy exclusion of symbols which was too aggressive

the goal was to avoid tutorial names appearing as namespaces.
The change removes from the doc also the tutorials, which is not
acceptable.

documentation/doxygen/Doxyfile

@@ -990,8 +990,7 @@ EXCLUDE_PATTERNS       = */G__* \
 # exclude all test directories use the pattern */test/*
 
 EXCLUDE_SYMBOLS        = std \
-                         cling* \
-                         rf*_*
+                         cling*
 
 # The EXAMPLE_PATH tag can be used to specify one or more files or directories
 # that contain example code fragments that are included (see the \include