- Copy stable/10@296371 to releng/10.3 in preparation for 10.3-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.3.
- Update default pkg(8) configuration to use the quarterly branch.

Approved by: re (implicit)

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)

Move prototypes of various encoding-related functions into a new header
file to avoid extern'ing them all over the place.

Allow partial multibyte characters to accumulate in conversion state
objects passed to mbrtowc(), mbsrtowcs(), and mbrlen(), as required
by C99.

Implement the ISO C90 Amd.1 restartable wide and multibyte character
manipulation functions mbrlen(), mbrtowc(), mbsinit(), mbsrtowcs(),
wcrtomb(), wcsrtombs().