preferring -qlanglvl=extc89 to -qlanglvl=ansi with IBM's compiler

[Paul Eggert]

To follow up to the current discussion in address@hidden, I installed
this patch:

2004-12-02  Paul Eggert  <address@hidden>

        * lib/autoconf/c.m4 (_AC_PROG_CC_STDC): Prefer -qlanglvl=extc89
        to -qlanglvl=ansi.  We don't want to disable extensions.

--- c.m4        20 Aug 2004 07:01:02 -0000      1.190
+++ c.m4        2 Dec 2004 20:09:03 -0000       1.191
@@ -864,12 +864,14 @@ char **argv;]],
 [[return f (e, argv, 0) != argv[0]  ||  f (e, argv, 1) != argv[1];]])])
 # Don't try gcc -ansi; that turns off useful extensions and
 # breaks some systems' header files.
-# AIX                  -qlanglvl=ansi
+# AIX circa 2003       -qlanglvl=extc89
+# old AIX              -qlanglvl=ansi
 # Ultrix, OSF/1, Tru64 -std
 # HP-UX 10.20 and later        -Ae
 # HP-UX older versions -Aa -D_HPUX_SOURCE
 # SVR4                 -Xc -D__EXTENSIONS__
-for ac_arg in "" -qlanglvl=ansi -std -Ae "-Aa -D_HPUX_SOURCE" "-Xc 
-D__EXTENSIONS__"
+for ac_arg in "" -qlanglvl=extc89 -qlanglvl=ansi -std \
+       -Ae "-Aa -D_HPUX_SOURCE" "-Xc -D__EXTENSIONS__"
 do
   CC="$ac_save_CC $ac_arg"
   _AC_COMPILE_IFELSE([],