Const poison a couple of interfaces.

Obtained from: lua boot project
Sponsored by: Netflix

stand/common/bootstrap.h

@@ -49,10 +49,10 @@ void	interact(const char *rc);
 int	include(const char *filename);
 
 /* interp_backslash.c */
-char	*backslash(char *str);
+char	*backslash(const char *str);
 
 /* interp_parse.c */
-int	parse(int *argc, char ***argv, char *str);
+int	parse(int *argc, char ***argv, const char *str);
 
 /* interp_forth.c */
 void	bf_init(const char *rc);

stand/common/interp_backslash.c

@@ -28,7 +28,7 @@ __FBSDID("$FreeBSD$");
  * processing" done on it.  Original can be free'd if desired.
  */
 char *
-backslash(char *str)
+backslash(const char *str)
 {
     /*
      * Remove backslashes from the strings. Turn \040 etc. into a single

stand/common/interp_parse.c

@@ -82,7 +82,7 @@ isdquote(int ch)
 }
 
 int
-parse(int *argc, char ***argv, char *str)
+parse(int *argc, char ***argv, const char *str)
 {
     int ac;
     char *val, *p, *q, *copy = NULL;