64-bit clean + WARNS=6:

- Convert the (char *) cast+cast backs magic to
	  memcpy(3).  Without this, the resulting code
	  is potentially risky with higher optimization
	  levels.
	- Avoid same name when calling local variables,
	  as well as global symbols.  This reduces
	  confusion for both human and compiler.
	- Add necessary casts, consts
	- Use new style function defination.
	- Minor style.Makefile(5) tweak
	- Bump WARNS?= from 0 to 6

** for the aout code: changes are intentionally limited
   to ease maintaince.

libexec/rtld-aout/shlib.c

@@ -62,14 +62,13 @@
 char	 **search_dirs;
 int	n_search_dirs;
 
-char	*standard_search_dirs[] = {
+const char	*standard_search_dirs[] = {
 	STANDARD_SEARCH_DIRS
 };
 
 
 void
-add_search_dir(name)
-	char	*name;
+add_search_dir(const char *name)
 {
 	int n;
 
@@ -269,7 +268,7 @@ search_lib_dir(dir, name, majorp, minorp, do_dot_a)
 	int		*minorp;
 	int		do_dot_a;
 {
-	int		namelen;
+	size_t		namelen;
 	DIR		*dd;
 	struct dirent	*dp;
 	int		best_dewey[MAXDEWEY];

libexec/rtld-aout/shlib.h

@@ -33,7 +33,7 @@
 extern char	**search_dirs;
 extern int	n_search_dirs;
 
-void	add_search_dir __P((char *));
+void	add_search_dir __P((const char *));
 void	add_search_path __P((char *));
 void	std_search_path __P((void));
 int	getdewey __P((int[], char *));