[ticket/12213] Add MCP events for custom quick moderation options

Add core events to mcp.php and mcp_main.php. This allows
extensions to add and to handle custom quick moderation options.

PHPBB3-12213
Merge pull request #2045 from rxu/ticket/12213

[ticket/12213] Add MCP events for custom quick moderation options
[ticket/12190] Add core event "core.modify_submit_post_data"
Add core event - core.modify_submit_post_data
to submit_post() function. This allows extensions to modify the
whole post data before the post submitting, or even provide
its own post submit procedure.

PHPBB3-12190
Merge pull request #2030 from rxu/ticket/12190

Add core event "core.modify_submit_post_data"
[ticket/12153] Replace old template variables with {PAGE_NUMBER}.

PHPBB3-12153
Merge pull request #2047 from prototech/ticket/12153

[ticket/12153] Replace old template variables with {PAGE_NUMBER}.