fix($compile): support transcluding multi-element directives

[gkalpak]

Do you want to request a feature or report a bug?

Bug.

What is the current behavior?
Transcluding multi-element directives (e.g. ng-repeat-start/ng-repeat-end) is not supported on elements with multi-slot transclusion and a $compile:uterdir error is thrown.
Originally reported by @jamie-pate in #14653 (comment).

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem via https://plnkr.co or similar (template: http://plnkr.co/edit/tpl:yBpEi4).
Reproduction.

What is the expected behavior?
Multi-element directives should be transcluded correctly on elements with multi-slot transclusion and without throwing.

Which versions of Angular, and which browser / OS are affected by this issue? Did this work in previous versions of Angular? Please also test with the latest stable and snapshot (https://code.angularjs.org/snapshot/) versions.

Affects all Angular versions since a least 1.5.0 (including 1.6.x/master).