Enable basic command line editing in evbarm, sparc64 and vax installer shells

(Following the pattern in amd64)

When a user selects "exit installer" or hits ^Z in sysinst, the
calling install.sh runs a shell, plus shows a message indicating
they can type "exit" to return to the installer.

Add -E to the arguments to this shell, to enable command line editing,
(primarily for arrow keys, but basic emacs sequences will also work)

With the change of all the install.sh scripts in amd64, evbarm,
i386, sparc64 and vax are identical apart from NetBSD RCD tags and
the sysctl -nx kern.consdev check (some of the latter are definitely
either wrong, or have an incorrect comment attached. Will return
to later)

branches: 1.2.26;
Make sure to copy the language catalog files for sysinst, but do not
copy sysinst itself to / on the CD, and instead use the base version
for installation.

branches: 1.1.2; 1.1.6;
Use GENERIC instead of INSTALL (including the ramdisk) for this CD image
and mount the CD filesystem as root instead for installation.