add SDKs for 10.1.5, 10.2.8, and 10.3.0
make the SDKs for 10.4u and 10.5 more closely match what I actually had on my computer

I'm guessing the "*.o" files must have been missing previously because
the previous committer must have gitignored "*.o" files globally or
something. This should NOT be done with this repo, because the "*.o"
files are actually part of the toolchain here.