Standardise header include guards

Tokens that begin with two underscores __* or an underscore and an uppercase letter _X* are reserved,
so we should avoid those for our own include guards.  The standard I'm settling on for foo.h is FOO_H_.

include/translat.h

@@ -5,9 +5,8 @@
  *
  * @(#)$Id$
  */
-
-#ifndef __translat_h_
-#define __translat_h_
+#ifndef TRANSLAT_H_
+#define TRANSLAT_H_
 
 	void	set_translation (Window *, char *, int);
 	void	enter_digraph (char, char *);
@@ -27,4 +26,4 @@ extern	unsigned char	dig_table_di[DIG_TABLE_SIZE];
 extern	char	digraph_hit;
 extern	unsigned char	digraph_first;
 
-#endif /* __translat_h_ */
+#endif /* TRANSLAT_H_ */