ffafcd8819
This involves lots of breaking changes. There are two big changes that force changes. The first is that the bitflag types now don't automatically implement normal derive traits, so we need to derive them manually. Additionally, bitflags now have a hidden inner type by default, which breaks our custom derives. The bitflags docs recommend using the impl form in these cases, which I did.
rustc_target contains some very low-level details that are
specific to different compilation targets and so forth.
For more information about how rustc works, see the rustc dev guide.