Document the use of <tag>

Add support for @pre as found in BuildFileTest

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@467363 13f79535-47bb-0310-9956-ffa450edef68

build.xml

@@ -1487,6 +1487,7 @@
 
       <packageset dir="${java.dir}"/>
 
+      <!-- hide some meta information for javadoc -->
       <tag name="todo" description="To do:" scope="all"/>
       <tag name="ant.task" enabled="false" description="Task:" scope="types"/>
       <tag name="ant.datatype" enabled="false" description="Data type:" scope="types"/>
@@ -1515,6 +1516,9 @@
       windowtitle="${Name} Test Utilities"
       doctitle="${Name}">
 
+      <!-- hide some meta information for javadoc -->
+      <tag name="pre" description="Precondition:" scope="all"/>
+
       <fileset dir="${src.junit}">
         <patternset refid="useful.tests"/>
       </fileset>