Detect endianness at configuration with Autoconf AC_C_BIGENDIAN feature

configure.ac

@@ -103,6 +103,12 @@ if test $have___thread = yes; then
 fi
 AC_MSG_RESULT($have___thread)
 
+AC_C_BIGENDIAN(
+   AC_DEFINE([IEEE_MC68k], 1, [machine is bigendian]),
+   AC_DEFINE([IEEE_8087], 1, [machine is littleendian]),
+   AC_MSG_ERROR(unknown endianess),
+   AC_MSG_ERROR(universial endianess not supported)
+)
 
 AC_SUBST([BUNDLER], ["$bundle_cmd"])