Re-define the order of #includes because MPI's C++ bindings

unfortunately redefined some C library constants (SEEK_SET, SEEK_CUR,
SEEK_END).  Scheesh -- who designed those bindings, anyway?

Most <stdio.h>'s and <iostream>'s are sane enough that if those values
are already #define'd, they won't redefine them.  So various other
MPI's out there have counseled that if you want to compile with the
C++ MPI bindings, ensure to include "mpi.h" before <iostream> or
<stdio.h> (in C++ source files).

This commit was SVN r11511.

examples/hello_cxx.cc

@@ -7,8 +7,15 @@
 // Sample MPI "hello world" application in C++
 //
 
-#include <iostream>
+// MPI's C++ bindings unfortunately redefined some POSIX constants
+// (SEEK_SET and friends).  Fortunately, most versions of <iostream>
+// and <stdio.h> are sane enough that if you include "mpi.h" first,
+// they won't redefine the problematic values.  Note, however, that
+// this means that you should not make calls to fseek(3) (and friends)
+// in a C++ source file that includes <mpi.h>!
+
 #include "mpi.h"
+#include <iostream>
 
 int main(int argc, char **argv)
 {

examples/ring_cxx.cc

@@ -7,8 +7,15 @@
 // Simple ring test program
 //
 
-#include <iostream>
+// MPI's C++ bindings unfortunately redefined some POSIX constants
+// (SEEK_SET and friends).  Fortunately, most versions of <iostream>
+// and <stdio.h> are sane enough that if you include "mpi.h" first,
+// they won't redefine the problematic values.  Note, however, that
+// this means that you should not make calls to fseek(3) (and friends)
+// in a C++ source file that includes <mpi.h>!
+
 #include "mpi.h"
+#include <iostream>
 
 int main(int argc, char *argv[])
 {