Add comments to sax APIs:

for processingInstruction method in XFastDocumentHandler
and for XFastNamespaceHandler API.

Change-Id: Ie0fd8ceb42e7ffbce041796b98edaa7f232dbb62
Reviewed-on: https://gerrit.libreoffice.org/38964
Reviewed-by: Mohammed Abdul Azeem <azeemmysore@gmail.com>
Tested-by: Mohammed Abdul Azeem <azeemmysore@gmail.com>

offapi/com/sun/star/xml/sax/XFastDocumentHandler.idl

@@ -51,6 +51,7 @@ interface XFastDocumentHandler: XFastContextHandler
 
 
     /** receives notification of a processing instruction.
+        @since LibreOffice 6.0
      */
     void processingInstruction( [in] string aTarget, [in] string aData )
             raises( com::sun::star::xml::sax::SAXException );

offapi/com/sun/star/xml/sax/XFastNamespaceHandler.idl

@@ -23,12 +23,24 @@
 
 module com {  module sun {  module star {  module xml {  module sax {
 
-/** @since LibreOffice 5.3 */
+/** Stores and manages namespace declarations of a sax
+    document parsed by XFastParser.
+
+    @since LibreOffice 5.3
+ */
 interface XFastNamespaceHandler: com::sun::star::uno::XInterface
 {
+
+    /** receives notification of namespace declarations
+        from a XFastParser.
+     */
     void registerNamespace( [in] string NamespacePrefix, [in] string NamespaceURI );
 
+
+    /** retrieves the namespace URI of a namespace prefix
+     */
     string getNamespaceURI( [in] string NamespacePrefix );
+
 };