Bug 176681 Issue about creating context-parameter path in read-only path[0601]
Description: Issue about creating context-parameter path in read-only path Build number:2.2.0.v20070308 Steps to reproduce: 1. Deploy birt. 2. Set BIRT_VIEWER_DOCUMENT_FOLDER/BIRT_VIEWER_IMAGE_DIR/.. to a read-only path. 3. Preview report. Expected result: Because the path is read-only, folders should be created in ${java.io.tmpdir} Actual result: No folders are created in ${java.io.tmpdir} and reports cannot be previewed in frameset mode.
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/utility/ParameterAccessor.java
* URL parameter name that gives the page range to display the report.
	 */
	public static final String PARAM_PAGE_RANGE = "__pagerange"; 
	/**
	 * URL parameter name that gives the report design name.
	 */
	public static final String PARAM_ISNULL = "__isnull"; 
	/**
	 * URL parameter name that indicate the report parameter as a locale string.
	 */
	public static final String PARAM_ISLOCALE = "__islocale"; 
	/**
	 * URL parameter name that determines to support masterpage or not.
	 */
	public static final String PARAM_MASTERPAGE = "__masterpage"; 
	/**
	 * URL parameter name that determines whether the BIRT application is
	 * running in the designer or standalone.
	 */
	public static final String PARAM_DESIGNER = "__designer"; 
	/**
	 * URL parameter name that determines whether to overwrite the document or
	 * not.
	 */
	public static final String PARAM_OVERWRITE = "__overwrite"; 
	/**
	 * URL parameter name that gives the image ID to display.
	 */
	public static final String PARAM_IMAGEID = "__imageID"; 
	/**