Add re-exports to use suggestions

In the following example, an inaccessible path is suggested via
`use foo::bar::X;` whereas an accessible public exported path can
be suggested instead.

```
mod foo {
    mod bar {
        pub struct X;
    }
    pub use self::bar::X;
}

fn main() { X; }
```

This fixes the issue.

src/test/ui/glob-resolve1.rs

@@ -29,3 +29,7 @@ fn main() {
     foo::<C>(); //~ ERROR: cannot find type `C` in this scope
     foo::<D>(); //~ ERROR: cannot find type `D` in this scope
 }
+
+mod other {
+    pub fn import() {}
+}

src/test/ui/glob-resolve1.stderr

@@ -42,6 +42,11 @@ error[E0425]: cannot find function `import` in this scope
    |
 LL |     import();
    |     ^^^^^^ not found in this scope
+   |
+help: consider importing this function
+   |
+LL | use other::import;
+   |
 
 error[E0412]: cannot find type `A` in this scope
   --> $DIR/glob-resolve1.rs:28:11

src/test/ui/namespace/namespace-mix.stderr

@@ -16,7 +16,7 @@ help: consider importing one of these items instead
    |
 LL | use m2::S;
    |
-LL | use namespace_mix::xm2::S;
+LL | use xm2::S;
    |
 
 error[E0423]: expected value, found type alias `xm1::S`
@@ -39,7 +39,7 @@ help: consider importing one of these items instead
    |
 LL | use m2::S;
    |
-LL | use namespace_mix::xm2::S;
+LL | use xm2::S;
    |
 
 error[E0423]: expected value, found struct variant `m7::V`
@@ -61,7 +61,7 @@ help: consider importing one of these items instead
    |
 LL | use m8::V;
    |
-LL | use namespace_mix::xm8::V;
+LL | use xm8::V;
    |
 
 error[E0423]: expected value, found struct variant `xm7::V`
@@ -83,7 +83,7 @@ help: consider importing one of these items instead
    |
 LL | use m8::V;
    |
-LL | use namespace_mix::xm8::V;
+LL | use xm8::V;
    |
 
 error[E0277]: the trait bound `c::Item: Impossible` is not satisfied

src/test/ui/resolve/issue-21221-2.stderr

@@ -4,7 +4,9 @@ error[E0405]: cannot find trait `T` in this scope
 LL | impl T for Foo { }
    |      ^ not found in this scope
    |
-help: consider importing this trait
+help: consider importing one of these items
+   |
+LL | use baz::T;
    |
 LL | use foo::bar::T;
    |

src/test/ui/resolve/privacy-enum-ctor.stderr

@@ -132,7 +132,7 @@ LL |     let _: E = m::n::Z;
    |            ^
 help: consider importing this enum
    |
-LL | use m::n::Z;
+LL | use m::Z;
    |
 
 error[E0423]: expected value, found enum `m::n::Z`
@@ -165,7 +165,7 @@ LL |     let _: E = m::n::Z::Fn;
    |            ^
 help: consider importing this enum
    |
-LL | use m::n::Z;
+LL | use m::Z;
    |
 
 error[E0412]: cannot find type `Z` in this scope
@@ -183,7 +183,7 @@ LL |     let _: E = m::n::Z::Struct;
    |            ^
 help: consider importing this enum
    |
-LL | use m::n::Z;
+LL | use m::Z;
    |
 
 error[E0423]: expected value, found struct variant `m::n::Z::Struct`
@@ -212,7 +212,7 @@ LL |     let _: E = m::n::Z::Unit {};
    |            ^
 help: consider importing this enum
    |
-LL | use m::n::Z;
+LL | use m::Z;
    |
 
 error[E0603]: enum `Z` is private