compiler: Wire {TyAnd,}Layout into rustc_abi

This finally unites TyAndLayout, Layout, and LayoutS into the same crate,
as one might imagine they would be placed. No functional changes.

compiler/rustc_target/src/lib.rs

@@ -21,8 +21,8 @@
 
 use std::path::{Path, PathBuf};
 
-pub mod abi;
 pub mod asm;
+pub mod callconv;
 pub mod json;
 pub mod spec;
 pub mod target_features;
@@ -30,6 +30,15 @@ pub mod target_features;
 #[cfg(test)]
 mod tests;
 
+pub mod abi {
+    pub(crate) use Float::*;
+    pub(crate) use Primitive::*;
+    // Explicitly import `Float` to avoid ambiguity with `Primitive::Float`.
+    pub use rustc_abi::{Float, *};
+
+    pub use crate::callconv as call;
+}
+
 pub use rustc_abi::HashStableContext;
 
 /// The name of rustc's own place to organize libraries.