agetty: Fix input of non-ASCII characters in get_logname()

agetty: Fix input of non-ASCII characters in get_logname()

As login supports non-ASCII characters in the logname, agetty should be
consistent.

8b58ffdd re-activated old and ASCII-only get_logname(), which restricted
the input to ASCII only. As the code does not read whole characters,
isascii(ascval) and isprint(ascval) returns nonsenses after entering a
non-ASCII character.

As keyboard maps don't contain unprintable non-control characters, it
seems to be relatively safe to remove both checks.

Signed-off-by: Stanislav Brabec <sbrabec@suse.cz>
Cc: Lubomir Rintel <lkundrak@v3.sk>
Tested-by: Lubomir Rintel <lkundrak@v3.sk>