doc improvement.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@4904 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/Launcher.java

@@ -88,6 +88,8 @@ public abstract class Launcher {
     }
 
     /**
+     * @param env
+     *      Environment variable overrides.
      * @param in
      *      null if there's no input.
      * @param workDir