Better error message for old-style AC_LANG

[Pavel Roskin]

Hello!

After some consideration I decided to take a minimal approach to the
problem of AC_LANG. The only thing that has changed is the error message
for the case when the first argument is empty.

Automatic updating of `CPLUSPLUS' and `FORTRAN77' may be dangerous.
AC_LANG was not documented in 2.13, so WYGIWYD (What you get is what you
deserve).

Besides, I don't feel that there should be only one name for the language
- we are already using two names internally - _AC_LANG and
_AC_LANG_ABBREV.

In short: this fix is essential. Everything else (AU_DEFUN, AC_LANG_NAME
etc) can be added if anybody really wants it.

Regards,
Pavel Roskin

__________________
Index: aclang.m4
--- aclang.m4   Tue Nov 14 09:00:01 2000
+++ aclang.m4   Thu Nov 23 20:10:36 2000
@@ -117,8 +117,10 @@
 # If you add quotes here, they will be part of the name too, yielding
 # `AC_LANG([C])' for instance, which does not exist.
 AC_DEFUN([AC_LANG],
-[m4_define([_AC_LANG], [$1])dnl
-_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])
+[ifval([$1],
+       [m4_define([_AC_LANG], [$1])dnl
+_AC_LANG_DISPATCH([$0], _AC_LANG, $@)],
+       [AC_FATAL([Don't use $0 with no arguments, use AC_LANG_CASE])])])


 # AC_LANG_PUSH(LANG)
__________________