- 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

For variables that are only checked with defined(), don't provide
any fake value.

Upgrade to Groff 1.19.

Removed now unused INTERNALSTATICLIB.
INTERNALLIB now implies NOPIC and NOPROFILE.
Removed gratuitous NOMAN.

Upgrade to Groff 1.17.