sysexit_.h fix

[Sergey Poznyakoff]

I propose the following change to sysexit_.h. Reason: if HAVE_SYSEXITS_H
is expanded to 1, then the included header file might be protected by
`#ifdef _SYSEXITS_H' (in fact, it is, on GNU/Linux) which will prevent
its contents from being included.

Index: lib/sysexit_.h
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/sysexit_.h,v
retrieving revision 1.4
diff -p -u -r1.4 sysexit_.h
--- lib/sysexit_.h      26 Mar 2007 10:16:08 -0000      1.4
+++ lib/sysexit_.h      30 Mar 2007 17:01:02 -0000
@@ -17,8 +17,8 @@
 
 /* Written by Simon Josefsson based on sysexits(3) man page */
 
-#ifndef _SYSEXITS_H
-#define _SYSEXITS_H
+#ifndef _GNULIB_SYSEXITS_H
+#define _GNULIB_SYSEXITS_H
 
 #if @HAVE_SYSEXITS_H@
 
@@ -51,4 +51,4 @@
 
 #endif
 
-#endif /* _SYSEXITS_H */
+#endif /* _GNULIB_SYSEXITS_H */