No filter to disable single forum description exists

[naxoc]

There is currently no way to avoid calculating all the stats for the "This forum has x topics, x replies, and was last updated x mins by x." above forums. There is already a filter to _alter_ it, but no way to avoid doing all those calculations.

Well, yes. There is a way by removing the call to bbp_single_forum_description() from templates, but it would be nice to be able to filter if it should happen.

This patch adds a bbp_use_single_forum_description filter that is checked before starting calling the function that gathers the data.

[johnjamesjacoby]

In 7970:

Forums/Topics: Allow descriptions to be disabled.

Add early filters to the single-forum and single-topic description getters so extensions can skip topic, reply, voice, freshness, and author calculations when these descriptions are not needed. Preserve each existing output filter by passing an empty default through it when generation is disabled.

In trunk, for 2.7.

Props naxoc.
Fixes #3488, #3489.