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

Fix malloc size (visible on amd64, with "kldconfig -r").

Sync program's usage() with manpage's SYNOPSIS.

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

Use __FBSDID() to quiet GCC 3.3 warnings.

style(9): use NULL when assigning/comparing a char *,
consitently compare fileid with 0 using == and !=.

Reviewed by: silence on @audit

Properly cast a size argument to an unsigned type.

Thanks to: dd for noticing the need for a cast.

Silence warnings on the Alpha: don't assume size_t is an int.

Add kldconfig(8), a utility to modify the kernel module search path.

Reviewed by: -arch, -audit