Bug 153853 [Regression]The bound column names must be unique within the entire table.
Regression case Regression_136421(under org.eclipse.birt.report.tests.model) failed. Expected result: Model will avoid adding a duplicate bound column name within a table.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/ModuleHandle.java
* 
 * <tr>
 * <td>Code Modules</td>
 * <td>Global scripts that apply to the report as a whole.</td>
 * </tr>
 * 
 * <tr>
 * <td>Parameters</td>
 * <td>A list of Parameter elements that describe the data that the user can
 * enter when running the report.</td>
 * </tr>
 * 
 * <tr>
 * <td>Data Sources</td>
 * <td>The connections used by the report.</td>
 * </tr>
 * 
 * <tr>
 * <td>Data Sets</td>
 * <td>Data sets defined in the design.</td>
 * </tr>
 * 
 * <tr>
 * <td>Color Palette</td>
 * <td>A set of custom color names as part of the design.</td>
 * </tr>
 * 
 * <tr>
 * <td>Styles</td>
 * <td>User-defined styles used to format elements in the report. Each style