Fix error in format argument specifiers.

Invoking generator com.google.gwt.uibinder.rebind.UiBinderGenerator
[ERROR] Generator 'com.google.gwt.uibinder.rebind.UiBinderGenerator' threw an
exception while rebinding
java.util.MissingFormatArgumentException: Format specifier '3$s'
at java.util.Formatter.format(Formatter.java:2454)
at java.util.Formatter.format(Formatter.java:2383)
at java.lang.String.format(String.java:2781)
at com.google.gwt.uibinder.rebind.MortalLogger.die(MortalLogger.java:92)
at com.google.gwt.uibinder.rebind.UiBinderWriter.die(UiBinderWriter.java:678)
at
com.google.gwt.uibinder.elementparsers.DockLayoutPanelParser.parse(DockLayoutPanelParser.java:83)

presubmit results here:
http://test/ui#id=OCL:27307574:BASE:27308011:1328317433551:bb4c07f9

Review by: rchandia@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@10870 8db76d5a-ed1c-0410-87a9-c151d255dfc7