add docuemntation hooks

doc/starpu.texi

@@ -293,6 +293,8 @@ TODO
 * SCHED     :: Scheduling policy
 * CALIBRATE :: Calibrate performance models
 * PREFETCH  :: Use data prefetch
+* STARPU_SCHED_ALPHA  :: Computation factor
+* STARPU_SCHED_BETA  :: Communication factor
 @end menu
 
 @node SCHED
@@ -322,6 +324,24 @@ TODO
 
 @end table
 
+@node STARPU_SCHED_ALPHA
+@subsection @code{STARPU_SCHED_ALPHA} -- Computation factor
+@table @asis
+
+@item @emph{Description}:
+TODO
+
+@end table
+
+@node STARPU_SCHED_BETA
+@subsection @code{STARPU_SCHED_BETA} -- Communication factor
+@table @asis
+
+@item @emph{Description}:
+TODO
+
+@end table
+
 @node Misc
 @section Miscellaneous and debug