* Only use default control content template when a more specific template doesn't exist.
* Remove extraneous whitespace from being output in `WP_Customize_Control::render()` method.
* Move Custom Header template printing to `customize_controls_print_footer_scripts` action.
See #30738.
Built from https://develop.svn.wordpress.org/trunk@41935
git-svn-id: http://core.svn.wordpress.org/trunk@41769 1a063a9b-81f0-0310-95a4-ce76da25c4cd