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
* Context parameter name that gives preview report max rows limited.
	 */
	public static final String INIT_PARAM_VIEWER_MAXROWS = "BIRT_VIEWER_MAX_ROWS"; 
	/**
	 * Context parameter name that if always overwrite generated document file.
	 */
	public static final String INIT_PARAM_OVERWRITE_DOCUMENT = "BIRT_OVERWRITE_DOCUMENT"; 
	/**
	 * Context parameter name that defines BIRT viewer configuration file.
	 */
	public static final String INIT_PARAM_CONFIG_FILE = "BIRT_VIEWER_CONFIG_FILE"; 
	/**
	 * UTF-8 encode constants.
	 */
	public static final String UTF_8_ENCODE = "UTF-8"; 
	/**
	 * ISO-8859-1 encode constants.
	 */
	public static final String ISO_8859_1_ENCODE = "ISO-8859-1"; 
	/**
	 * Separator that connects the query parameter values.
	 */
	public static final String PARAMETER_SEPARATOR = "&"; 
	/**
	 * The character to start the query string in the url.
	 */
	public static final String QUERY_CHAR = "?"; 
	/**
	 * Equals operator.
	 */