extend to the bottom of the sea (merge from devbr6)

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@36828 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/gis/colors/srtm

@@ -1,3 +1,4 @@
+-11000 0 0 0
 -500 0 0 10
 -300 0 0 20
 -200 0 0 70