MFC r258355,258360,258400-258401,258406-258407,258418,258430,258439,258589-

MFC r258355,258360,258400-258401,258406-258407,258418,258430,258439,258589-
258590,258592,258727-258728,258785, with the following descriptions:

Revisions 258400-258401,258406-258407,258590,258727-258728,258785:
+ Add a new `includes' module (see: bsdconfig includes -h) for exploring
  the bsdconfig(8) API

Remaining revisions:
258592: Sort all the messages.subr files
258355: Fix typo in a comment in networking/device.subr
258360: Whitespace, style, and other changes in networking/device.subr
258418: Quote interface names for good measure in networking/device.subr
258430: Remove an unused line in networking/device.subr
258439: Minor bugfix to f_die() function in common.subr
258589: Minor bugfix to syscons_ttys module

git-svn-id: svn://svn.freebsd.org/base/stable/10@260675 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f