block: when loading gpt labels, if the partition name does not
pass out validation engine, then set it to an empty string.
ui_newt: remove minimum password length checks. it shall now only test
that it is non-empty.
ui_newt: replace data checks in user/root config
also use general error text macros for these 2.
ui_newt: use new is_dns_label in ui_window_host
remove some more utility functions which are converted to re2c
re2ctest: add tests for is_utf8_locale
re2ctest: add tests for is_user_name