Better choice if profile-end water depth is less than depth of closure

[davefavismortlock]

See create_profiles.cpp c. line 475. Currently, if the water depth at the profile end point is less than the depth of closure, we do nothing (i.e. we carry on and create the profile normally). A better choice would be to extend -- if possible -- the profile. There may also be other possible courses of action, needs discussion.

[davefavismortlock]

This is also related, see c. line 544 in profile.cpp. Previously this function returned the index of the cell on the profile which has a sea depth which is just less than a given depth. If every cell on the profile has a sea depth which is less than the given depth it returned INT_NODATA. However this was modified (to make long runs more robust) so that if every cell on the profile has a sea depth which is less than the given depth, then it just returns the (almost) end of profile depth. This may need to be a permanent change, but again it should be discussed.