Teach acpidump(8) to display the 'Flags' field in the HPET Description Table.

Reviewed by:	jhb@
Style: don't compare unsigned <= 0.

Sponsored by:	Nginx, Inc.
Eliminate redundant information about the host cpu in bhyve's KTR trace points.
This is always tracked by ktr(4) and can be displayed using the "-c" option
of ktrdump(8).

Discussed with:	grehan
Fix off by ones when scanning source nodes hash.

Sponsored by:	Nginx, Inc.
Add missing 'extern'.
To support upcoming changes change internal API for source node handling:
- Removed pf_remove_src_node().
- Introduce pf_unlink_src_node() and pf_unlink_src_node_locked().
  These function do not proceed with freeing of a node, just disconnect
  it from storage.
- New function pf_free_src_nodes() works on a list of previously
  disconnected nodes and frees them.
- Utilize new API in pf_purge_expired_src_nodes().

In collaboration with:	Kajetan Staszkiewicz <kajetan.staszkiewicz innogames.de>

Sponsored by:	InnoGames GmbH
Sponsored by:	Nginx, Inc.