Copy stable/11@r303970 to releng/11.0 as part of the 11.0-RELEASE
cycle.

Prune svn:mergeinfo from the new branch, and rename it to RC1.

Update __FreeBSD_version.

Use the quarterly branch for the default FreeBSD.conf pkg(8) repo and
the dvd1.iso packages population.

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

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Remove some unneeded headers

Found by 'include-what-you-use'

Cleanup a bit includes

Rewrite parsing subcommands arguments of pw(8)

Now each subcommands checks its arguments in a dedicated functions.

This helps improving input validation, code readability/maintainability
While here:
- Add a -y option to pw userdel/usermod so it can maintain NIS servers if
nispasswd is not defined in pw.conf(5)
- Allow pw -r <rootdir> to remove directory with userdel -r
- Fix bug when renaming a user which was not renaming the user name it groups
it is a member of.
- Only parse pw.conf(5) when needed.