10.4/10.5 SDKs in Project Settings

[pointum]

The project still has code and references to the old SDKs:

This causes this warning:
libarclite_macosx.a(arclite.o)) was built for newer OSX version (10.6) than being linked (10.5)

I thought this commit is supposed to drop anything below 10.6. I could make a PR that removes obsolete settings and code.