Merge pull request #281 from nealef/s390x

Add support for s390x

checks/architecture/Jamroot.jam

@@ -22,3 +22,4 @@ obj power    : power.cpp ;
 obj riscv    : riscv.cpp ;
 obj sparc    : sparc.cpp ;
 obj x86      : x86.cpp ;
+obj s390x    : s390x.cpp ;

checks/architecture/s390.cpp

@@ -0,0 +1,11 @@
+// s390x.cpp
+//
+// Copyright (c) 2012 Steven Watanabe
+//
+// Distributed under the Boost Software License Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#if !defined(__s390x__)
+#error "Not S390x"
+#endif