fix JavaDoc warnings [no description for @param]

Author: cpoerschke

src/main/java/org/junit/internal/runners/statements/FailOnTimeout.java

@@ -106,7 +106,7 @@ public Builder withLookingForStuckThread(boolean enable) {
          * Builds a {@link FailOnTimeout} instance using the values in this builder,
          * wrapping the given statement.
          *
-         * @param statement
+         * @param statement statement to build
          */
         public FailOnTimeout build(Statement statement) {
             if (statement == null) {

src/main/java/org/junit/runner/JUnitCore.java

@@ -63,7 +63,7 @@ public static Result runClasses(Computer computer, Class<?>... classes) {
     }
 
     /**
-     * @param system
+     * @param system system to run with
      * @param args from main()
      */
     Result runMain(JUnitSystem system, String... args) {