make this useable from c++.

lib/libedit/histedit.h

@@ -1,4 +1,4 @@
-/*	$NetBSD: histedit.h,v 1.26 2005/05/07 16:01:25 dsl Exp $	*/
+/*	$NetBSD: histedit.h,v 1.27 2005/06/12 06:58:21 christos Exp $	*/
 
 /*-
  * Copyright (c) 1992, 1993
@@ -46,6 +46,10 @@
 #include <sys/types.h>
 #include <stdio.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /*
  * ==== Editing ====
  */
@@ -212,4 +216,8 @@ int		 tok_line(Tokenizer *, const LineInfo *,
 int		 tok_str(Tokenizer *, const char *,
 		    int *, const char ***);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _HISTEDIT_H_ */