- 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)

MFC r260310:

libcpp: misc fixes from Apple's GCC.

Fixes some bugs detected by Apple:
#error with unmatched quotes
pragma mark

Obtained from: Apple GCC 4.2 - 5553

MFC r258826, r259555, r 259558:

libcpp: Merge fixes from upstream
Fixes:
GCC preprocessor/29966:
GCC preprocessor/28709:
GCC c/31924
GCC preprocessor/14331

gcc: add Apple-compatible -Wnewline-eof

Obtained from: gcc per-4.3 (rev. 121340, 124356, 124358, 124730,
125212, 125255 ; GPLv2)
Apple Inc. (Apple GCC 4.2 - 5531)

gcc: add Apple compatible -Wnewline-eof

GCC 4.2 and previous have always warned about
"No newline at end of file".

Upstream GCC removed the warning completely but
Apple made it an optional warning. Adopt it for
compatibility with older GCC and clang.

While here, add comment to complement r258712.

Obtained from: Apple Inc. (Apple GCC 4.2 - 5531)
MFC after: 1 week