auto merge of #16575 : pcwalton/rust/import-foo-as-bar, r=aturon

of `use bar as foo`.

Change all uses of `use foo = bar` to `use bar as foo`.

Implements RFC #47.

Closes #16461.

[breaking-change]

r? @aturon

src/doc/rust.md

@@ -1801,7 +1801,7 @@ module through the rules above. It essentially allows public access into the
 re-exported item. For example, this program is valid:
 
 ~~~~
-pub use api = self::implementation;
+pub use self::implementation as api;
 
 mod implementation {
     pub fn f() {}

src/doc/tutorial.md

@@ -3112,7 +3112,7 @@ use farm::*;
 However, that's not all. You can also rename an item while you're bringing it into scope:
 
 ~~~
-use egg_layer = farm::chicken;
+use farm::chicken as egg_layer;
 # mod farm { pub fn chicken() { println!("Laying eggs is fun!")  } }
 // ...
 
@@ -3335,7 +3335,7 @@ you just have to import it with an `use` statement.
 For example, it re-exports `range` which is defined in `std::iter::range`:
 
 ~~~
-use iter_range = std::iter::range;
+use std::iter::range as iter_range;
 
 fn main() {
     // `range` is imported by default