(version_etc_copyright): Declare as readonly.
(version_etc_va): New function. Provide a different translatable string
for each possible number of authors < 10. Abbreviate when there are 10
authors or more.
(version_etc): Make this function variadic. Call version_etc_va.
`Written by ...' part of --version output.
Include stdarg.h, stdlib.h, string.h, and xalloc.h.
(version_etc): Make this function variadic,
with a NULL-terminated list of author name strings.
(version_etc_va): New function.
of copyright with `%s' so translators don't get an untranslated message in 2002.
(COPYRIGHT_YEAR): Define.
(version_etc): Use fprintf rather than fputs.
