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

Cleanup elf macros

Only define EF_MIPS_ABI when not already supplied
Remove old now unused ARM macros

Reported by: imp
Approved by: re (kib)

More -Wmissing-variable-declarations fixes.

In addition to adding `static' where possible:

- bin/date: Move `retval' into extern.h to make it visible to date.c.
- bin/ed: Move globally used variables into ed.h.
- sbin/camcontrol: Move `verbose' into camcontrol.h and fix shadow warnings.
- usr.bin/calendar: Remove unneeded variables.
- usr.bin/chat: Make `line' local instead of global.
- usr.bin/elfdump: Comment out unneeded function.
- usr.bin/rlogin: Use _Noreturn instead of __dead2.
- usr.bin/tset: Pull `Ospeed' into extern.h.
- usr.sbin/mfiutil: Put global variables in mfiutil.h.
- usr.sbin/pkg: Remove unused `os_corres'.
- usr.sbin/quotaon, usr.sbin/repquota: Remove unused `qfname'.

add usr.sbin/pkg which is a bootstrap tool for pkgng.
it respects PACKAGESITE, PACKAGEROOT, and a new environment variable ABI (if a user want to use a different API from the base one for its packages)
it has no man page on purpose to avoid hidding the pkg(8) man page from the pkgng package.
for now uses pkgbeta.FreeBSD.org as default mirror to find its package
it respects MK_PKGTOOLS

Approved by: des (mentor)