New file. From Adam Thornton <athornton@sinenomine.net>.

src/m/ibms390.h

+/* machine description file template.
+   Copyright (C) 1985, 1986, 2001 Free Software Foundation, Inc.
+
+This file is part of GNU Emacs.
+
+GNU Emacs is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Emacs is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Emacs; see the file COPYING.  If not, write to
+the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+Boston, MA 02111-1307, USA.  */
+
+
+/* The following line tells the configuration script what sort of 
+   operating system this machine is likely to run.
+   USUAL-OPSYS="<name of system .h file here, without the s- or .h>"  */
+
+/* Define WORDS_BIG_ENDIAN iff lowest-numbered byte in a word
+   is the most significant byte.  */
+
+#define WORDS_BIG_ENDIAN
+
+/* Define NO_ARG_ARRAY if you cannot take the address of the first of a
+ * group of arguments and treat it as an array of the arguments.  */
+
+#define NO_ARG_ARRAY
+
+/* Define WORD_MACHINE if addresses and such have
+ * to be corrected before they can be used as byte counts.  */
+
+#define WORD_MACHINE
+
+/* Now define a symbol for the cpu type, if your compiler
+   does not define it automatically:
+   Ones defined so far include vax, m68000, ns16000, pyramid,
+   orion, tahoe, APOLLO and many others */
+
+#define s390
+
+/* Use type int rather than a union, to represent Lisp_Object */
+/* This is desirable for most machines.  */
+
+#define NO_UNION_TYPE
+
+/* Define EXPLICIT_SIGN_EXTEND if XINT must explicitly sign-extend
+   the 24-bit bit field into an int.  In other words, if bit fields
+   are always unsigned.
+
+   If you use NO_UNION_TYPE, this flag does not matter.  */
+
+#define EXPLICIT_SIGN_EXTEND
+
+/* Data type of load average, as read out of kmem.  */
+
+#define LOAD_AVE_TYPE long
+
+/* Convert that into an integer that is 100 for a load average of 1.0  */
+
+#define LOAD_AVE_CVT(x) (int) (((double) (x)) * 100.0 / FSCALE)
+
+/* Define CANNOT_DUMP on machines where unexec does not work.
+   Then the function dump-emacs will not be defined
+   and temacs will do (load "loadup") automatically unless told otherwise.  */
+
+/* #define CANNOT_DUMP */
+
+/* Define VIRT_ADDR_VARIES if the virtual addresses of
+   pure and impure space as loaded can vary, and even their
+   relative order cannot be relied on.
+
+   Otherwise Emacs assumes that text space precedes data space,
+   numerically.  */
+
+#define VIRT_ADDR_VARIES
+
+/* Define C_ALLOCA if this machine does not support a true alloca
+   and the one written in C should be used instead.
+   Define HAVE_ALLOCA to say that the system provides a properly
+   working alloca function and it should be used.
+   Define neither one if an assembler-language alloca
+   in the file alloca.s should be used.  */
+
+/* #define C_ALLOCA */
+#define HAVE_ALLOCA
+
+/* Define NO_REMAP if memory segmentation makes it not work well
+   to change the boundary between the text section and data section
+   when Emacs is dumped.  If you define this, the preloaded Lisp
+   code will not be sharable; but that's better than failing completely.  */
+
+/*#define NO_REMAP */
+
+/* Some really obscure 4.2-based systems (like Sequent DYNIX)
+ * do not support asynchronous I/O (using SIGIO) on sockets,
+ * even though it works fine on tty's.  If you have one of
+ * these systems, define the following, and then use it in
+ * config.h (or elsewhere) to decide when (not) to use SIGIO.
+ *
+ * You'd think this would go in an operating-system description file,
+ * but since it only occurs on some, but not all, BSD systems, the
+ * reasonable place to select for it is in the machine description
+ * file.
+ */
+
+/*#define NO_SOCK_SIGIO*/
+
+
+/* After adding support for a new system, modify the large case
+   statement in the `configure' script to recognize reasonable
+   configuration names, and add a description of the system to
+   `etc/MACHINES'.
+
+   If you've just fixed a problem in an existing configuration file,
+   you should also check `etc/MACHINES' to make sure its descriptions
+   of known problems in that configuration should be updated.  */