Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Add Bluetooth compatibility shims. Inspired by Linux BlueZ and NetBSD.

Discussed with: Iain Hibbert plunky -at- rya-online -dot- net of NetBSD
MFC after: 1 month

Make NULL a (void*)0 whereever possible, and fix the warnings(-Werror)
that this provokes. "Wherever possible" means "In the kernel OR NOT
C++" (implying C).

There are places where (void *) pointers are not valid, such as for
function pointers, but in the special case of (void *)0, agreement
settles on it being OK.

Most of the fixes were NULL where an integer zero was needed; many
of the fixes were NULL where ascii <nul> ('\0') was needed, and a
few were just "other".

Tested on: i386 sparc64

Update Bluetooth code.

Reviewed by: M. Warner Losh <imp@bsdimp.com>; John Hay <jhay@freebsd.org>
Approved by: M. Warner Losh <imp@bsdimp.com> (mentor)