* configure.ac: Use AC_PROG_CC_STDC, not just AC_PROG_CC. Remove obsolete macros AC_ISC_POSIX, AC_HEADER_SYS_WAIT, AC_HEADER_DIRENT, AC_HEADER_STAT, AC_HEADER_STDC, AC_TYPE_SIGNAL, AC_TYPE_SIZE_T. * lib/prepargs.c (IN_CTYPE_DOMAIN): Remove. All uses removed. * src/list.c (from_header): Use isspace, not ISSPACE. * src/system.c (pipe_handler, sys_exec_info_script): * src/tar.c (sigstat): Use void, not RETSIGTYPE.