doc: document environment variables STARPU_MIN_PRIO and STARPU_MAX_PRIO

doc/doxygen/chapters/40environment_variables.doxy

@@ -1,7 +1,7 @@
 /*
  * This file is part of the StarPU Handbook.
  * Copyright (C) 2009--2011  Universit@'e de Bordeaux
- * Copyright (C) 2010, 2011, 2012, 2013, 2014, 2015  CNRS
+ * Copyright (C) 2010, 2011, 2012, 2013, 2014, 2015, 2016  CNRS
  * Copyright (C) 2011, 2012 INRIA
  * See the file version.doxy for copying conditions.
  */
@@ -336,6 +336,20 @@ random, stealing, greedy, with performance models, etc.
 Use <c>STARPU_SCHED=help</c> to get the list of available schedulers.
 </dd>
 
+<dt>STARPU_MIN_PRIO</dt>
+<dd>
+\anchor STARPU_MIN_PRIO_env
+\addindex __env__STARPU_MIN_PRIO
+Set the mininum priority used by priorities-aware schedulers.
+</dd>
+
+<dt>STARPU_MAX_PRIO</dt>
+<dd>
+\anchor STARPU_MAX_PRIO_env
+\addindex __env__STARPU_MAX_PRIO
+Set the maximum priority used by priorities-aware schedulers.
+</dd>
+
 <dt>STARPU_CALIBRATE</dt>
 <dd>
 \anchor STARPU_CALIBRATE