Found with https://github.com/est31/warnalyzer.
Dubious changes:
- Is anyone else using rustc_apfloat? I feel weird completely deleting
x87 support.
- Maybe some of the dead code in rustc_data_structures, in case someone
wants to use it in the future?
- Don't change rustc_serialize
I plan to scrap most of the json module in the near future (see
https://github.com/rust-lang/compiler-team/issues/418) and fixing the
tests needed more work than I expected.
TODO: check if any of the comments on the deleted code should be kept.
Reduce memory consumption by taking advantage of red/green algorithm
properties to share the previous dependency graph's node data with the
current graph instead of storing node data redundantly. Red nodes can
share the `DepNode`, and green nodes can share the `DepNode` and
`Fingerprint`. Edges will be shared when possible in a later change.
