Remove whitespace at end of string "Scan boot sectors".
Update config.guess and config.sub to latest. (Freshly from GNU's repo)
configure.ac: Replace the obsolete AC_HELP_STRING with AS_HELP_STRING
configure.ac: Replace the obsolete AM_CONFIG_HEADER with AC_CONFIG_HEADERS
configure.ac: Replace the obsolete AC_LANG_C with AC_LANG([C])
configure.ac: Remove AM_SANITY_CHECK which shouldn't be called directly.
configure.ac: Clarify the meaning of 'HAVE_PRCTL' C macro.
Correct zh_CN and zh_TW translation about the '-k' switch.