- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

Implement xlocale APIs from Darwin, mainly for use by libc++. This adds a
load of _l suffixed versions of various standard library functions that use
the global locale, making them take an explicit locale parameter. Also
adds support for per-thread locales. This work was funded by the FreeBSD
Foundation.

Please test any code you have that uses the C standard locale functions!

Reviewed by: das (gdtoa changes)
Approved by: dim (mentor)

Introduce a local variable and use it instead of passed in parameter
to get rid of restrict qualifier discarding. This lets libc compile
cleanly in gnu99 mode.

Suggested by: kib, christoph.mallon at gmx.de
Approved by: kib (mentor)

Implement the GNU extensions of mbsnrtowcs() and wcsnrtombs(). These are
convenient when the source string isn't null-terminated.

Implement the other conversion functions (mbstowcs(), mbsrtowcs(), wcstombs(),
wcsrtombs()) in terms of these new functions.

Allow encoding modules to override the default implementations of
mbsrtowcs() and wcsrtombs(). Provide a fast implementation for the
trivial "NONE" encoding.

Begin in the initial shift state in mbstowcs() and wcstombs().
(This change is non-functional since nothing uses states yet.)

Prepare to handle state-dependent encodings. This mainly involves not
taking shortcuts when it comes to storing and passing around conversion
states.

Implement mbstowcs() as a wrapper around mbsrtowcs(), and wcstombs()
as a wrapper around wcsrtombs().

Style sweep.

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

Add restrict qualifiers to the arguments of mbstowcs, mbtowc() and
wcstombs().

Implement the XSI extension which allows the destination string to be
NULL, and returns the number of bytes that would be required to store
the result of the conversion without storing anything.

PR: 17694

Split ansi.c into a separate source file for each function.