dnl
dnl Ensure that Expat is configured with autoconf 2.58 or newer
-AC_PREREQ(2.58)
+AC_PREREQ(2.69)
dnl Get the version number of Expat, using m4's esyscmd() command to run
dnl the command at m4-generation time. This allows us to create an m4
dnl defines it to 4321 when the platform is big endian.
dnl
dnl A long time ago (early 2000 years) AC_C_BIGENDIAN was considered wrong
-dnl when cross compiling, now (2018) we assume it is fine.
+dnl when cross compiling, now (2018, GNU Autoconf 2.69) we assume it is fine.
AC_C_BIGENDIAN([BYTEORDER=4321],[BYTEORDER=1234])
AC_DEFINE_UNQUOTED(BYTEORDER, $BYTEORDER, [1234 = LILENDIAN, 4321 = BIGENDIAN])