improve appearance of gui's dcoumentation browser * arrow_down.png, arrow_left.png, arrow_right.png: new image files * arrow_up.png, redled.png, bookmark.png: updated image files * file_editor_tab.cc(constructor): use bookmark.png as marker for actual line * module.mk: new image files * resource.qrc: new image files * parser.cc(replace_links): prevent linebreaks within node-links, smaller bookmark icons; (replace_colons): enclosed words are formatted bold and blue; (info_to_html): 'Menu' bold, underlined; 'See also' italic, darkred; (node_text_to_html): news icon for anchor of searched function and general navigation, select a monospace font for preformatted text sections; (global_search): smaller bookmark icons;

--- a/libgui/src/m-editor/file-editor-tab.cc
+++ b/libgui/src/m-editor/file-editor-tab.cc
@@ -89,7 +89,7 @@
   _edit_area->markerDefine (QsciScintilla::RightTriangle, bookmark);
   _edit_area->markerDefine (QPixmap (":/actions/icons/redled.png"),
                             breakpoint);
-  _edit_area->markerDefine (QPixmap (":/actions/icons/arrow_right.png"),
+  _edit_area->markerDefine (QPixmap (":/actions/icons/bookmark.png"),
                             debugger_position);
 
   connect (_edit_area, SIGNAL (marginClicked (int, int,