Auto merge of rust-lang#51333 - GuillaumeGomez:reexport-fmt-alignment, r=SimonSapin

Reexport fmt::Alignment into std

Follow-up of rust-lang#51078.

Author: bors

src/liballoc/fmt.rs

@@ -531,6 +531,8 @@ pub use core::fmt::Error;
 pub use core::fmt::{write, ArgumentV1, Arguments};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::fmt::{DebugList, DebugMap, DebugSet, DebugStruct, DebugTuple};
+#[stable(feature = "fmt_flags_align", since = "1.28.0")]
+pub use core::fmt::{Alignment};
 
 use string;
 

src/libcore/fmt/mod.rs

@@ -1436,8 +1436,7 @@ impl<'a> Formatter<'a> {
     /// ```
     /// extern crate core;
     ///
-    /// use std::fmt;
-    /// use core::fmt::Alignment;
+    /// use std::fmt::{self, Alignment};
     ///
     /// struct Foo;
     ///