[m-rev.] for review: Commit java as Error should not fill in stack trace

[Maxime Van Assche]

As far as I can tell, using Throwable for Commit does not require the stack trace.
However, the default constructor of Error constructs the stack trace, which is costly.

java/runtime/Commit.java :
	Override fillInStackTrace to do nothing

diff --git a/java/runtime/Commit.java b/java/runtime/Commit.java
index a5f875ba..8cd0b68 100644
--- a/java/runtime/Commit.java
+++ b/java/runtime/Commit.java
@@ -9,6 +9,10 @@
 package jmercury.runtime;

 public class Commit extends java.lang.Error {
+    public Throwable fillInStackTrace() {
+        // do nothing, for performance reasons.
+        return this;
+    }

 }