- 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

Provide sysarch(2) prototypes in the MD sysarch.h headers. While I'm
at it, use the ANSI C generic pointer type for the second argument,
thus matching the documentation.

Remove the now extraneous (and now conflicting) function declarations
in various libc sources. Remove now unnecessary casts.

Reviewed by: bde

Add implementations of amd64_[gs]et_[fg]sbase().