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

Use the "builtin" shell function to make sure that the requested
command is handled as a shell function. This avoids the following
peculiar behaviour when /usr/bin is on a case-insensitive filesystem:
# READ foo
(... long pause, depending upon the amount of swap space available ...)
sh: Resource temporarily unavailable.

Reported by: I can't remember; someone on IRC.
MFC after: 1 week

A little bit more thought has resulted in a generic script which can
implement any of the useless POSIX-required ``regular shell builtin''
utilities, saving one frag and one inode each. The script moves to
usr.bin/alias which is alphabetically the first of these commands.