Some improvements on the header view layout. It puts finally the

Some improvements on the header view layout. It puts finally the
priority icon in its place
* src/maemo/modest-icon-names.h:
        * Added standard high and low priority icons, to be used
          from the custom icon renderers in thumbable headers.
* src/widgets/modest-header-view-render.c:
	* Use the proper icons for high and low priority, instead
	  of the old composed ones used for the shared priority and
	  attachments cell renderer (fixes NB#62262).
* src/widgets/modest-header-view.c:
	* Some other layout fixes in compact header view.

pmo-trunk-r2760