[ticket/12930] core.ucp_pm_compose_compose_pm_quotepost_query_after

Adding the core.ucp_pm_compose_compose_pm_quotepost_query_after
event to ucp backend.

https://tracker.phpbb.com/browse/PHPBB3-12930

PHPBB3-12930
It can be informative. I don't know... I thought it could be useful depending on the extension.
For my purpose, it is useless.