Allow phutil_render_tag() to accept an array content argument

Summary: D4509 converted some `phutil_render_tag('x', array(...), $x.$y)` to `phutil_tag('x', array(...), array($x, $y))`, but we don't currently support this. Support it, since it makes conversions easier.

Test Plan: Fixes some issues in the `phutil_tag` branch, like `PhabricatorPropertyListView`.

Reviewers: vrana

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D4640