Even more SNAP cleanup.

…r-chosen names.

cc rust-lang-nursery/thanks#71

Unignore u128 test for stage 0,1

Even more SNAP cleanup.

Follow-up of rust-lang#39519.

Sorry, I didn't check twice.

…ata, r=alexcrichton

Choose different name for metadata obj-file to avoid clashes with user-chosen names.

Fixes rust-lang#39585 and probably rust-lang#39508.
Incremental compilation assigns different names to obj-files than regular compilation. If a crate is called "metadata" this can lead to a clash between the root module's obj-file and the obj-file containing crate-metadata. This PR assigns a name to the metadata obj-file that cannot clash with other obj-file because it contains a `.` which is not allowed in a Rust module identifier.

r? @alexcrichton

cc @nikomatsakis

…=steveklabnik

Fix mailmap for @gifnksm

cc rust-lang-nursery/thanks#71

…erister

Exclude top-level macro expansions from source location override.

It occurred to me that a simple heuristic can address the issue rust-lang#36382: any macros that expand into items (including `include!()`) don't need to be stepped over because there's not code to step through above a function scope level.

r? @michaelwoerister

Fix unsafe unaligned loads in test.

r? @eddyb
cc @Aatch @nikomatsakis

The `#[derive(PartialEq, Debug)]` impls on a packed struct contain undefined behaviour. Both generated impls take references to unaligned fields, which will fail to compile once we correctly treat that as unsafe (see rust-lang#27060).

This UB was found by running the test under [Miri](https://github.com/solson/miri/) which rejects these unsafe unaligned loads. 😄

Here's a simpler example:

```rust
struct Packed {
    a: u8,
    b: u64,
}
```

It expands to:

```rust
    fn fmt(&self, __arg_0: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
        match *self {
            Packed { a: ref __self_0_0, b: ref __self_0_1 } => { // BAD: these patterns are unsafe
                let mut builder = __arg_0.debug_struct("Packed");
                let _ = builder.field("a", &&(*__self_0_0));
                let _ = builder.field("b", &&(*__self_0_1));
                builder.finish()
            }
        }
    }
```

and

```rust
    fn eq(&self, __arg_0: &Packed) -> bool {
        match *__arg_0 {
            Packed { a: ref __self_1_0, b: ref __self_1_1 } => // BAD: these patterns are unsafe
            match *self {
                Packed { a: ref __self_0_0, b: ref __self_0_1 } => // BAD: these patterns are unsafe
                true && (*__self_0_0) == (*__self_1_0) &&
                    (*__self_0_1) == (*__self_1_1),
            },
        }
    }
```

…metadata, r=bluss

Fix unaligned load in librustc_metadata::index.

The derived `Clone` impl contains UB and will be unsafe when we fix rust-lang#27060. See [this comment](rust-lang#27060 (comment)) for more context.

r? @bluss