all: check stdout and stderr status at exit

If stream status is not checked at the end of execution below problem
would not report error, or non-zero exit code.  The uptime is just an
example same was true with all commands of the project.

$ uptime >&- ; echo $?
uptime: write error: Bad file descriptor
1
$ uptime >/dev/full ; echo $?
uptime: write error: No space left on device
1

Signed-off-by: Sami Kerola <kerolasa@iki.fi>

sysctl.c

@@ -40,6 +40,7 @@
 #include <unistd.h>
 
 #include "c.h"
+#include "fileutils.h"
 #include "nls.h"
 #include "xalloc.h"
 #include "proc/procps.h"
@@ -675,6 +676,7 @@ int main(int argc, char *argv[])
 	setlocale(LC_ALL, "");
 	bindtextdomain(PACKAGE, LOCALEDIR);
 	textdomain(PACKAGE);
+	atexit(close_stdout);
 
 	PrintName = true;
 	PrintNewline = true;