Test for presence of sysexits.h and set HAVE_SYSEXITS_H if so.  Used
by posixmodule.c.
diff --git a/pyconfig.h.in b/pyconfig.h.in
index eba68f6..3627b83 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -467,6 +467,9 @@
 /* Define to 1 if you have the `sysconf' function. */
 #undef HAVE_SYSCONF
 
+/* Define to 1 if you have the <sysexits.h> header file. */
+#undef HAVE_SYSEXITS_H
+
 /* Define to 1 if you have the <sys/audioio.h> header file. */
 #undef HAVE_SYS_AUDIOIO_H