Cray J90 fixes for long ints.

This was a convenient excuse to create the pyport.h file recently
discussed!
Please use new Py_ARITHMETIC_RIGHT_SHIFT when right-shifting a
signed int and you *need* sign-extension.  This is #define'd in
pyport.h, keying off new config symbol SIGNED_RIGHT_SHIFT_ZERO_FILLS.
If you're running on a platform that needs that symbol #define'd,
the std tests never would have worked for you (in particular,
at least test_long would have failed).
The autoconfig stuff got added to Python after my Unix days, so
I don't know how that works.  Would someone please look into doing
& testing an auto-config of the SIGNED_RIGHT_SHIFT_ZERO_FILLS
symbol?  It needs to be defined if & only if, e.g., (-1) >> 3 is
not -1.

Include/pyport.h

@@ -0,0 +1,57 @@
+/***********************************************************
+Copyright (c) 2000, BeOpen.com.
+All rights reserved.
+
+See the file "Misc/COPYRIGHT" for information on usage and
+redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
+******************************************************************/
+
+#ifndef Py_PYPORT_H
+#define Py_PYPORT_H 1
+
+/**************************************************************************
+Symbols and macros to supply platform-independent interfaces to basic
+C-language operations whose spellings vary across platforms.
+
+Please try to make documentation here as clear as possible:  by definition,
+the stuff here is trying to illuminate C's darkest corners.
+
+Config #defines referenced here:
+
+SIGNED_RIGHT_SHIFT_ZERO_FILLS
+Meaning:  To be defined iff i>>j does not extend the sign bit when i is a
+          signed integral type and i < 0.
+Used in:  Py_ARITHMETIC_RIGHT_SHIFT
+**************************************************************************/
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Py_ARITHMETIC_RIGHT_SHIFT
+ * C doesn't define whether a right-shift of a signed integer sign-extends
+ * or zero-fills.  Here a macro to force sign extension:
+ * Py_ARITHMETIC_RIGHT_SHIFT(TYPE, I, J)
+ *    Return I >> J, forcing sign extension.
+ * Requirements:
+ *    I is of basic signed type TYPE (char, short, int, long, or long long).
+ *    TYPE is one of char, short, int, long, or long long, although long long
+ *    must not be used except on platforms that support it.
+ *    J is an integer >= 0 and strictly less than the number of bits in TYPE
+ *    (because C doesn't define what happens for J outside that range either).
+ * Caution:
+ *    I may be evaluated more than once.
+ */
+#ifdef SIGNED_RIGHT_SHIFT_ZERO_FILLS
+#define Py_ARITHMETIC_RIGHT_SHIFT(TYPE, I, J) \
+	((I) < 0 ? ~((~(unsigned TYPE)(I)) >> (J)) : (I) >> (J))
+#else
+#define Py_ARITHMETIC_RIGHT_SHIFT(TYPE, I, J) ((I) >> (J))
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* Py_PYPORT_H */