Added test for uintptr_t, the C9X acceptable way to spell "type to

which I can cast void* to and back again without losing information".
In pyport.h, we typedef Py_uintptr_t to mean this thing, which if the
platform supports, will be uintptr_t (otherwise, other accomodations
are made).

config.h.in

@@ -124,6 +124,9 @@
 /* Define this if you have the type long long */
 #undef HAVE_LONG_LONG
 
+/* Define this if you have the type uintptr_t */
+#undef HAVE_UINTPTR_T
+
 /* Define if your compiler supports function prototypes */
 #undef HAVE_PROTOTYPES
 
@@ -254,6 +257,9 @@
 /* The number of bytes in a short.  */
 #undef SIZEOF_SHORT
 
+/* The number of bytes in a uintptr_t.  */
+#undef SIZEOF_UINTPTR_T
+
 /* The number of bytes in a void *.  */
 #undef SIZEOF_VOID_P
 

configure.in

@@ -399,6 +399,14 @@ if test "$have_long_long" = yes ; then
 AC_CHECK_SIZEOF(long long)
 fi
 
+AC_MSG_CHECKING(for uintptr_t support)
+have_uintptr_t=no
+AC_TRY_COMPILE([], [uintptr_t x; x = (uintptr_t)0;], AC_DEFINE(HAVE_UINTPTR_T) have_uintptr_t=yes)
+AC_MSG_RESULT($have_uintptr_t)
+if test "$have_uintptr_t" = yes ; then
+AC_CHECK_SIZEOF(uintptr_t)
+fi
+
 # Hmph. AC_CHECK_SIZEOF() doesn't include <sys/types.h>.
 AC_MSG_CHECKING(size of off_t)
 AC_CACHE_VAL(ac_cv_sizeof_off_t,