Bump beaver version to 0.9.11, so builds terminate on errors.

compiler/build.xml

@@ -20,7 +20,7 @@
 <!-- "jflex" is an ant task class for the scanner generator in JFlex.jar -->
 <taskdef name="jflex" classname="JFlex.anttask.JFlexTask" classpath="tools/JFlex.jar"/>
 <!-- "beaver" is an ant task class for the parser generator in beaver.jar -->
-<taskdef name="beaver" classname="beaver.comp.run.AntTask" classpath="tools/beaver.jar"/>
+<taskdef name="beaver" classname="beaver.comp.run.AntTask" classpath="tools/beaver-ant.jar"/>
 <!-- "jastadd" is an ant task class in jastadd2.jar -->
 <taskdef name="jastadd" classname="jastadd.JastAddTask"
 classpath="tools/jastadd2.jar"/>