add a patched osg_ocean

The patch fixes some dependency discovery issues, and installs
a pkg-config file.
osg_ocean: modify how resources are found

It now uses the default osgDB::Registry handling, that is looking
through OSG_FILE_PATH. This assumes that the resources are within
an osgOcean/shaders and osgOcean/textures subdirectories in
OSG_FILE_PATH
add vizkit3d_ocean
Merge pull request #1 from Brazilian-Institute-of-Robotics/osg_ocean

add a patched osg_ocean