Build fix: gwt-user uses the 2.4 servlet API spec.

git-svn-id: https://google-web-toolkit.googlecode.com/svn/releases/1.6@3917 8db76d5a-ed1c-0410-87a9-c151d255dfc7
diff --git a/user/build.xml b/user/build.xml
index 3cb3045..130e952 100755
--- a/user/build.xml
+++ b/user/build.xml
@@ -49,6 +49,7 @@
     <gwt.javac srcdir="test" excludes="com/google/gwt/langtest/**" destdir="${javac.junit.out}">
       <classpath>
         <pathelement location="${javac.out}" />
+        <pathelement location="${gwt.tools.lib}/tomcat/servlet-api-2.4.jar" />
         <pathelement location="${gwt.build}/out/dev/core/bin-test" />
         <pathelement location="${gwt.tools.lib}/junit/junit-3.8.1.jar" />
         <pathelement location="${gwt.tools.lib}/selenium/selenium-java-client-driver.jar" />