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

Per Regents of the University of Calfornia letter, remove advertising
clause.

# If I've done so improperly on a file, please let me know.

MFp4: Add the standard "the {fgetws,fputws} function will fail if" text
to the Errors section.

Style: One space between "restrict" qualifier and "*".

Basic support for wide character I/O: getwc(), fgetwc(), getwchar(),
putwc(), fputwc(), putwchar(), ungetwc(), fwide().