Merge branch '2.7' into 2.8

* 2.7:
  [travis/appveyor] Wire simple-phpunit
  [Console] fixed PHP7 Errors are now handled and converted to Exceptions
  Fix #19721
  bumped Symfony version to 2.7.19
  updated VERSION for 2.7.18
  update CONTRIBUTORS for 2.7.18
  updated CHANGELOG for 2.7.18
  [Security] Optimize RoleHierarchy's buildRoleMap method

Author: fabpot

Core/Role/RoleHierarchy.php

@@ -65,9 +65,17 @@ protected function buildRoleMap()
                 }
 
                 $visited[] = $role;
-                $this->map[$main] = array_unique(array_merge($this->map[$main], $this->hierarchy[$role]));
-                $additionalRoles = array_merge($additionalRoles, array_diff($this->hierarchy[$role], $visited));
+
+                foreach ($this->hierarchy[$role] as $roleToAdd) {
+                    $this->map[$main][] = $roleToAdd;
+                }
+
+                foreach (array_diff($this->hierarchy[$role], $visited) as $additionalRole) {
+                    $additionalRoles[] = $additionalRole;
+                }
             }
+
+            $this->map[$main] = array_unique($this->map[$main]);
         }
     }
 }