Rollup merge of rust-lang#33656 - GuillaumeGomez:lifetime_bound, r=steveklabnik

Add lifetime's bounds in doc generation

Fixes rust-lang#33653

![screenshot from 2016-05-15 15 30 38](https://cloud.githubusercontent.com/assets/3050060/15274445/024dbd5c-1ab2-11e6-9387-274301a05627.png)

r? @steveklabnik

Author: eddyb

src/librustdoc/clean/mod.rs

@@ -795,7 +795,17 @@ impl Clean<Lifetime> for hir::Lifetime {
 
 impl Clean<Lifetime> for hir::LifetimeDef {
     fn clean(&self, _: &DocContext) -> Lifetime {
-        Lifetime(self.lifetime.name.to_string())
+        if self.bounds.len() > 0 {
+            let mut s = format!("{}: {}",
+                                self.lifetime.name.to_string(),
+                                self.bounds[0].name.to_string());
+            for bound in self.bounds.iter().skip(1) {
+                s.push_str(&format!(" + {}", bound.name.to_string()));
+            }
+            Lifetime(s)
+        } else {
+            Lifetime(self.lifetime.name.to_string())
+        }
     }
 }