Improvements:
- Use Clone not Copy for the "simple cases"
- Separate TypeFoldable and Lift for the "simple cases"
- Support generics type parameters
- Support named fields in enum variants
- etc
... as single "internal compiler error" entry point.
The macros pass `file!()`, `line!()` and `format_args!(...)` on to a
cold, never-inlined function, ultimately calling `bug()` or `span_bug()`
on the `Handler` from `session::diagnostic()` via the tcx in tls or,
failing that, panicking directly.
This commit removes all the old casting/generic traits from `std::num` that are
no longer in use by the standard library. This additionally removes the old
`strconv` module which has not seen much use in quite a long time. All generic
functionality has been supplanted with traits in the `num` crate and the
`strconv` module is supplanted with the [rust-strconv crate][rust-strconv].
[rust-strconv]: https://github.com/lifthrasiir/rust-strconv
This is a breaking change due to the removal of these deprecated crates, and the
alternative crates are listed above.
[breaking-change]
