MFC r285140:
r285140 (by oshogbo):

Add fdclose(3) function.

This function is equivalent to fclose(3) function except that it
does not close the underlying file descriptor.
fdclose(3) is step forward to make FILE structure private.

Reviewed by: wblock, jilles, jhb, pjd
Approved by: pjd (mentor)
Differential Revision: https://reviews.freebsd.org/D2697

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

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

Add mkostemp() and mkostemps().

These are like mkstemp() and mkstemps() but allow passing open(2) flags like
O_CLOEXEC.

Add an implementation of open_memstream() and open_wmemstream(). These
routines provide write-only stdio FILE objects that store their data in a
dynamically allocated buffer. They are a string builder interface somewhat
akin to a completely dynamic sbuf.

Reviewed by: bde, jilles (earlier versions)
MFC after: 1 month

Add fmemopen(3), an interface to get a FILE * from a buffer in memory, along
with the respective regression test.
See http://pubs.opengroup.org/onlinepubs/9699919799/functions/fmemopen.html

Reviewed by: cognet
Approved by: cognet

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)

Add dprintf() and vdprintf() from POSIX.1-2008. Like getline(),
dprintf() is a simple wrapper around another function, so we may as
well implement it. But also like getline(), we can't prototype it by
default right now because it would break too many ports.

- Add getdelim(), getline(), stpncpy(), strnlen(), wcsnlen(),
wcscasecmp(), and wcsncasecmp().
- Make some previously non-standard extensions visible
if POSIX_VISIBLE >= 200809.
- Use restrict qualifiers in stpcpy().
- Declare off_t and size_t in stdio.h.
- Bump __FreeBSD_version in case the new symbols (particularly
getline()) cause issues with ports.

Reviewed by: standards@

Retire the __fgetcookie(), __fgetpendout(), and __fsetfileno() accessors
as we aren't hiding FILE's internals anymore.

Add __fgetcookie(), __fgetpendout() and __fsetfileno() to the private
name space.

Move all the xprintf-related symbols to FBSDprivate_1.0.

Discussed with: deischen, kan, phk

Use C comments since we now preprocess these files with CPP.

Now that libc has fcloseall(), remove _cleanup() from the list
of FreeBSD private symbols.

Add fcloseall() to libc. This removes the need to export _cleanup().
Linux also provides an fcloseall() implementation.

Discussed on: arch

Add __collate_load_error and __collate_range_cmp to the list of
FBSDprivate locale symbols. These functions are needed by
libcompat.

Add _cleanup to the list of stdio FBSDprivate symbols. Some
third party applications use this. This will be removed and
replaced by fcloseall() once libc version is bumped.

Add _res to the list of resolv symbols.

Found by: portbuilder runs (thanks Kris!)

Add symbol maps and initial symbol version definitions to libc.

Reviewed by: davidxu