osgwwhich unable to find non-plugin libraries on OSX

```
Try:
  osgwwhich libosgUtil.2.8.2.dylib
You get "can't find" message.

Seems like the OSG function we're calling to locate the library is designed 
for plugins, not regular library files, and as a result OSG looks in the 
osgPlugins subdir, but not the parent dir.
```

Original issue reported on code.google.com by `SkewMat...@gmail.com` on 13 Nov 2009 at 5:31
