doc/chapters/mpi-support.texi: update doc for starpu_mpi_scatter_detached() and starpu_mpi_gather_detached()

doc/chapters/mpi-support.texi

@@ -487,18 +487,24 @@ execute them, or to send the required data).
 @node MPI Collective Operations
 @section MPI Collective Operations
 
-@deftypefun int starpu_mpi_scatter_detached (starpu_data_handle_t *@var{data_handles}, int @var{count}, int @var{root}, MPI_Comm @var{comm})
+@deftypefun int starpu_mpi_scatter_detached (starpu_data_handle_t *@var{data_handles}, int @var{count}, int @var{root}, MPI_Comm @var{comm}, {void (*}@var{scallback})(void *), {void *}@var{sarg}, {void (*}@var{rcallback})(void *), {void *}@var{rarg})
 Scatter data among processes of the communicator based on the ownership of
 the data. For each data of the array @var{data_handles}, the
 process @var{root} sends the data to the process owning this data.
 Processes receiving data must have valid data handles to receive them.
+On completion of the collective communication, the @var{scallback} function is
+called with the argument @var{sarg} on the process @var{root}, the @var{rcallback} function is
+called with the argument @var{rarg} on any other process.
 @end deftypefun
 
-@deftypefun int starpu_mpi_gather_detached (starpu_data_handle_t *@var{data_handles}, int @var{count}, int @var{root}, MPI_Comm @var{comm})
+@deftypefun int starpu_mpi_gather_detached (starpu_data_handle_t *@var{data_handles}, int @var{count}, int @var{root}, MPI_Comm @var{comm}, {void (*}@var{scallback})(void *), {void *}@var{sarg}, {void (*}@var{rcallback})(void *), {void *}@var{rarg})
 Gather data from the different processes of the communicator onto the
 process @var{root}. Each process owning data handle in the array
 @var{data_handles} will send them to the process @var{root}. The
 process @var{root} must have valid data handles to receive the data.
+On completion of the collective communication, the @var{rcallback} function is
+called with the argument @var{rarg} on the process @var{root}, the @var{scallback} function is
+called with the argument @var{sarg} on any other process.
 @end deftypefun
 
 @page