[RFC|Implemented] adm_page_headeradm_page_footer override

[Erik Frèrejean]

Name: core.adm_page_header_override - core.adm_page_header_override
Rationale: Reasoning is the same as for the 'normal' page_header and page_footer override hooks. Ref: viewtopic.php?f=111&t=42741
Placement: /includes/functions_acp.php
Input arguments: The input arguments of the two functions as well the override flag, so for the `core.adm_page_header_override` event: $page_title, $adm_page_header_override and for the `core.adm_page_header_override` event: $copyright_html, $adm_page_footer_override

[Erik Frèrejean]

https://github.com/unknownbliss/phpbb3/pull/2

[MichaelC]

Implemented