Collapse three contiguous comment blocks into one. Remove historical
note about wrong assumptions 20 years ago. Use proper casing.

Sponsored by:	Nginx, Inc.
Re-work non-persistent filesystem detection as it was not possible to
detect /dev/md backed mfs filesystems that way.

Differential Revision:	https://reviews.freebsd.org/D1163
Approved by:	ian
Add Virtio MMIO bus driver.

Sponsored by:	DARPA, AFRL
Add Altera Parallel IO (PIO) device driver.

Sponsored by:	DARPA, AFRL
Missed a terminating ';'.

X-MFC-with:	r273009
Merge remote-tracking branch 'freebsd/master' into hardened/current/master