Add T*Executor and TTreeProcessorM{T,P} to the Parallelism group in Doxygen

core/imt/src/TThreadExecutor.cxx

@@ -4,6 +4,7 @@
 //////////////////////////////////////////////////////////////////////////
 ///
 /// \class ROOT::TThreadExecutor
+/// \ingroup Parallelism
 /// \brief This class provides a simple interface to execute the same task
 /// multiple times in parallel, possibly with different arguments every
 /// time. This mimics the behaviour of python's pool.Map method.

core/multiproc/src/TProcessExecutor.cxx

@@ -16,6 +16,7 @@
 //////////////////////////////////////////////////////////////////////////
 ///
 /// \class ROOT::TProcessExecutor
+/// \ingroup Parallelism
 /// \brief This class provides a simple interface to execute the same task
 /// multiple times in parallel, possibly with different arguments every
 /// time. This mimics the behaviour of python's pool.Map method.

tree/treeplayer/src/TTreeProcessorMP.cxx

@@ -17,6 +17,7 @@
 //////////////////////////////////////////////////////////////////////////
 ///
 /// \class ROOT::TTreeProcessorMP
+/// \ingroup Parallelism
 /// \brief This class provides an interface to process a TTree dataset
 ///        in parallel with multi-process technology
 ///

tree/treeplayer/src/TTreeProcessorMT.cxx

@@ -10,6 +10,7 @@
  *************************************************************************/
 
 /** \class ROOT::TTreeProcessorMT
+    \ingroup Parallelism
     \brief A class to process the entries of a TTree in parallel.
 
 By means of its Process method, ROOT::TTreeProcessorMT provides a way to process the