Change ASTPlugin to match the original a little more closely

src/org/eventb/internal/core/ast/ASTPlugin.java

 package org.eventb.internal.core.ast;
 
 public class ASTPlugin {
-	public static String PLUGIN_ID = "who.cares";
-	public static void log(Object who, Object cares) {}
+	public static final String PLUGIN_ID = "org.eventb.core.ast"; //$NON-NLS-1$
+
+	public static void log(Throwable exc, String message) {}
 }