[osg-submissions] osgDB::findDataFile doesn't honour search path

[Ulrich Hertlein]

Hi Robert,

Robert Osfield wrote:
> W.r.t zip loader, it should probably set its own local data search
> path lists, one that prepends any other search with its own.

If I read the code correctly this is just what it does (or attempts to do):
- clone the given ReaderWriter::Options or create a new one
- prepend the unpack directory to the new option's getDatabasePathList()
- attempt to load all files in the unpack directory, passing the
   options to the loader

This would work nicely *if* osgDB::findDataFile() wouldn't check for the 
given filename in the current directory before checking the database 
pathlist.

I'm similarly concerned that this might break peoples' apps so it's 
probably a good idea to float in on the osg-users -- I'll do that.

Cheers!
/ulrich