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.

fs.h

@@ -1,4 +1,24 @@
 /* See LICENSE file for copyright and license details. */
+#include <sys/types.h>
+
+struct history {
+        struct history *prev;
+        dev_t dev;
+        ino_t ino;
+};
+
+struct recursor {
+        void (*fn)(const char *, void *, struct recursor *);
+        struct history *hist;
+        int depth;
+        int follow;
+        int flags;
+};
+
+enum {
+        SAMEDEV = 1 << 0,
+};
+
 extern int cp_aflag;
 extern int cp_fflag;
 extern int cp_pflag;
@@ -11,5 +31,9 @@ extern int rm_fflag;
 extern int rm_rflag;
 extern int rm_status;
 
+extern int recurse_status;
+
+void recurse(const char *, void *, struct recursor *);
+
 int cp(const char *, const char *, int);
-void rm(const char *, int, void *);
+void rm(const char *, void *, struct recursor *);