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

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

correct description of how a string is stored, fix a few
typos and reference the kernel file which processes this info.

All in all, the content of this file should be moved to kldxref.c
or to the kld(4) manpage.

MFC after: 3 days

Add kldxref(8), for maintaining the linker.hints file for translating
module->pathname.ko. It supports only ELF for now.

Submitted by: bp (with some minor tweaks)