doc: fix syntax errors

doc/chapters/basic-api.texi

@@ -505,7 +505,7 @@ Sparse Row Representation) sparse matrix interface.
 TODO
 @end deftypefun
 
-@deftypefun void *starpu_data_get_interface_on_node (starpu_data_handle @var{handle}, unsigned @var{memory_node})
+@deftypefun {void *} starpu_data_get_interface_on_node (starpu_data_handle @var{handle}, unsigned @var{memory_node})
 todo
 @end deftypefun
 
@@ -605,11 +605,11 @@ This function is similar to @code{starpu_data_get_sub_data} but uses a
 va_list for the parameter list.
 @end deftypefun
 
-@deftypefun void starpu_data_map_filters(starpu_data_handle @var{root_data}, unsigned @var{nfilters}, ...)
+@deftypefun void starpu_data_map_filters (starpu_data_handle @var{root_data}, unsigned @var{nfilters}, ...)
 todo
 @end deftypefun
 
-@deftypefun void starpu_data_vmap_filters(starpu_data_handle @var{root_data}, unsigned @var{nfilters}, va_list @var{pa})
+@deftypefun void starpu_data_vmap_filters (starpu_data_handle @var{root_data}, unsigned @var{nfilters}, va_list @var{pa})
 todo
 @end deftypefun
 

doc/chapters/mpi-support.texi

@@ -212,7 +212,7 @@ transfers.
 Tell StarPU-MPI which MPI tag to use when exchanging the data.
 @end deftypefun
 
-@deftypefun int starpu_data_get_tag(starpu_data_handle @var{handle})
+@deftypefun int starpu_data_get_tag (starpu_data_handle @var{handle})
 Returns the MPI tag to be used when exchanging the data.
 @end deftypefun