Update to 2006.

src/tools/copyright

@@ -1,6 +1,6 @@
 rgrep -l 'Copyright.*PostgreSQL Global Development Group' | while read FILE
 do
-	pipe sed 's/^\(.*Copyright (c) [12][0-9][0-9][0-9]-\)[12][0-9][0-9][0-9]\(, PostgreSQL Global Development Group.*\)$/\12005\2/' $FILE
+	pipe sed 's/^\(.*Copyright (c) [12][0-9][0-9][0-9]-\)[12][0-9][0-9][0-9]\(, PostgreSQL Global Development Group.*\)$/\12006\2/' $FILE
 done
 
 echo "Manually update doc/src/sgml/legal.sgml too" 1>&2