We no longer need to include headers we don't use for sudo*.h files.

Previously we needed to include headers required by the various
sudo*h files.  Now those files are more self-sufficient and we
should only include headers needed by code in the various .c files.

plugins/sudoers/timestamp.c

@@ -23,7 +23,6 @@
 
 #include <config.h>
 
-#include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/ioctl.h>
 #include <stddef.h>
@@ -45,7 +44,6 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <pwd.h>
-#include <grp.h>
 #include <signal.h>
 
 #include "sudoers.h"