Define SIGPIPE for Windows, just for fixing the v1.4 Windows build.

cmr:v1.4.2:reviewer=jsquyres

This commit was SVN r22543.

opal/win32/win_compat.h

@@ -198,6 +198,7 @@ typedef unsigned int uint;
  */
 #define SIGCHLD SIGILL
 #define SIGKILL WM_QUIT
+#define SIGPIPE 13
 #define SIGCONT 18
 #define SIGSTOP 19
 #define SIGTSTP 20