Add the jm_GLIBC21 macro, required by AM_GNU_GETTEXT.

svn path=/trunk/vorbis-tools/; revision=3608

acinclude.m4

@@ -1078,3 +1078,32 @@ strdup strtoul tsearch __argz_count __argz_stringify __argz_next])
    INTL_LIBTOOL_SUFFIX_PREFIX=ifelse([$1], use-libtool, [l], [])
    AC_SUBST(INTL_LIBTOOL_SUFFIX_PREFIX)
   ])
+
+dnl this check it required by the gettext macro
+#serial 2
+
+# Test for the GNU C Library, version 2.1 or newer.
+# From Bruno Haible.
+
+AC_DEFUN([jm_GLIBC21],
+  [
+    AC_CACHE_CHECK(whether we are using the GNU C Library 2.1 or newer,
+      ac_cv_gnu_library_2_1,
+      [AC_EGREP_CPP([Lucky GNU user],
+	[
+#include <features.h>
+#ifdef __GNU_LIBRARY__
+ #if (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 1) || (__GLIBC__ > 2)
+  Lucky GNU user
+ #endif
+#endif
+	],
+	ac_cv_gnu_library_2_1=yes,
+	ac_cv_gnu_library_2_1=no)
+      ]
+    )
+    AC_SUBST(GLIBC21)
+    GLIBC21="$ac_cv_gnu_library_2_1"
+  ]
+)
+