Avoid using a leading underbar in defines as they are reserved in

ISO C.

include/sudo_fatal.h

@@ -14,8 +14,8 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
-#ifndef _SUDO_FATAL_H_
-#define	_SUDO_FATAL_H_
+#ifndef SUDO_FATAL_H
+#define	SUDO_FATAL_H
 
 #include <stdarg.h>
 #ifdef HAVE_STDBOOL_H
@@ -156,4 +156,4 @@ __dso_public void sudo_warn_set_conversation_v1(int (*conv)(int num_msgs, const
 # define sudo_warn_gettext(_a) sudo_warn_gettext_v1(NULL, (_a))
 #endif
 
-#endif /* _SUDO_FATAL_H_ */
+#endif /* SUDO_FATAL_H */