Use spaces, not tabs, in the Java and C# runtimes.

Add modelines to keep it that way.

Fix formatting, and english in comments.

java/runtime/Commit.java

@@ -1,10 +1,11 @@
+// vim: ts=4 sw=4 expandtab ft=java
 //
 // Copyright (C) 2002 The University of Melbourne.
 // Copyright (C) 2017-2018 The Mercury team.
 // This file is distributed under the terms specified in COPYING.LIB.
 //
 // This is a throwable class used for the Java implementation of commits.
-// 
+//
 
 package jmercury.runtime;