Bug 298835 Merge e4 Project Path Variable back into the 3.6 stream
The virtual folder and filters changes are already in 3.6, the project path variable changes in e4 still remains to be merged.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/dialogs/PathVariableDialog.java
* @return true if the name is valid, false otherwise
     */
    private boolean validateVariableName() {
        boolean allowFinish = false;
        if (operationMode == EDIT_LINK_LOCATION)
            return true;
        
        if (validationStatus == IMessageProvider.ERROR) {
			return false;
		}
        
        String message = standardMessage;
        int newValidationStatus = IMessageProvider.NONE;
        if (variableName.length() == 0) {
            
            if (nameEntered) {
                
                newValidationStatus = IMessageProvider.ERROR;
                message = IDEWorkbenchMessages.PathVariableDialog_variableNameEmptyMessage;
            }
        } else {
            IStatus status = pathVariableManager.validateName(variableName);
            if (!status.isOK()) {
                
                newValidationStatus = IMessageProvider.ERROR;
                message = status.getMessage();
            } else if (namesInUse.contains(variableName)
                    && !variableName.equals(originalName)) {
                
                message = IDEWorkbenchMessages.PathVariableDialog_variableAlreadyExistsMessage;