Add Reservoirs to water areas

[migurski]

Compare http://tile.stamen.com/terrain/preview.html#13/39.4533/-76.5642 and http://tile.stamen.com/toner/preview.html#13/39.4533/-76.5642

[nvkelso]

OSM decided to not add this as an optional
landuse=reservoir
modifying
natural=water

wtf.

<![CDATA[
(SELECT way,
name,
ST_Area(way) AS area
FROM planet_osm_polygon
WHERE "natural" IN ('water', 'bay')
OR waterway IN ('riverbank')
OR landuse IN ('reservoir')
ORDER BY z_order ASC, way_area DESC

            ) AS water]]></Parameter>