Add history and config-struct to recurse

For loop detection, a history is mandatory. In the process of also
adding a flexible struct to recurse, the recurse-definition was moved
to fs.h.
The motivation behind the struct is to allow easy extensions to the
recurse-function without having to change the prototypes of all
functions in the process.
Adding flags is really simple as well now.

Using the recursor-struct, it's also easier to see which defaults
apply to a program (for instance, which type of follow, ...).

Another change was to add proper stat-lstat-usage in recurse. It
was wrong before.

rm.c

@@ -11,6 +11,8 @@ usage(void)
 int
 main(int argc, char *argv[])
 {
+	struct recursor r = { .fn = rm, .hist = NULL, .depth = 0, .follow = 'P', .flags = 0};
+
 	ARGBEGIN {
 	case 'f':
 		rm_fflag = 1;
@@ -31,7 +33,7 @@ main(int argc, char *argv[])
 	}
 
 	for (; *argv; argc--, argv++)
-		rm(*argv, 0, NULL);
+		rm(*argv, NULL, &r);
 
-	return rm_status;
+	return rm_status || recurse_status;
 }