Set $ENV in the default skel/dot.cshrc as dot.profile for su(1) etc.

Fixes PR/59008. Worth to pullup to netbsd-10.

dot.cshrc: add commented out LESS example

Switch commented out PAGER from more(1), the default, to less(1), so
that a user can just uncomment the line and doesn't have to edit it.

While here, add commented out example of setting less(1) options with
LESS and explain how you can use -X to alleviate the pain from
alternate screen switching (b/c, of course, nothing is more user
friendly than wiping away from the screen the manual page you have
just been reading in your PAGER and want to peek at again as you are
typing the command).

This should have been in the same commit with the identical
dot.profile change.

branches: 1.8.14; 1.8.16;
/usr/X11R6 has been empty on most NetBSD installations since 2008,
and the last few straggling ports dumped it in 2015. It's time to
prune references to /usr/X11R6 from our config files.

branches: 1.7.36;
put back a commented out EXINIT entry.

Re-enable EDITOR=vi because otherwise stuff breaks. (Or runs ed, which
is arguably equivalent to breaking.)

Per the discussion on tech-userlevel, document the settings offered.

(All of this needs quite a bit more work still.)

Cleanup ancient entries derived from 4.4BSD Lite2 merge
for newer useradd(8) users:
- remove all aliases
- remove annoying EXINIT setting
- comment out other environment settings

Discussed on tech-userlevel@.

Sprinkle /usr/X11R7 where relevant. rc.d/x{fs,dm} are left to be done.

branches: 1.3.32; 1.3.40;
Add more descriptive header comments for default dotfiles.
Text based on suggestions by Igor Sobrado in PR misc/21223

Nuke 'umask 2' as it is inappropriate for the default useradd(8)
behaviour. The system default (022) is more sensible.

branches: 1.1.2; 1.1.4; 1.1.6;
Copy skel files from sharesrc/share/skel.

Part of fix for PR bin/10985.