Add viewtopic_body.html template event to allow custom post notices

Identifier: viewtopic_body_postrow_post_notices_before
Identifier: viewtopic_body_postrow_post_notices_after

Prosilver Location (if applicable): viewtopic_body.html, before and after the delete reason/edit reason/bumped message post notices.
Subsilver Location (if applicable): same.

Explanation: this event allows extensions to add own post specific info alike notices mentioned before do.
Use case: Some MODS/extensions add their own post specific information to particular posts. Example: thanks for posts MOD that adds an info about particular post thanks.