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.

tar.c

@@ -9,6 +9,7 @@
 #include <string.h>
 #include <unistd.h>
 
+#include "fs.h"
 #include "util.h"
 
 struct header {
@@ -234,10 +235,10 @@ print(char * fname, int l, char b[BLKSIZ])
 }
 
 static void
-c(const char *path, int depth, void *data)
+c(const char *path, void *data, struct recursor *r)
 {
 	archive(path);
-	recurse(path, c, depth, NULL);
+	recurse(path, NULL, r);
 }
 
 static void
@@ -266,6 +267,7 @@ int
 main(int argc, char *argv[])
 {
 	FILE *fp;
+	struct recursor r = { .fn = c, .hist = NULL, .depth = 0, .follow = 'P', .flags = 0};
 	struct stat st;
 	char *file = NULL, *dir = ".", mode = '\0';
 
@@ -293,7 +295,7 @@ main(int argc, char *argv[])
 		filtermode = ARGC();
 		break;
 	case 'h':
-		recurse_follow = 'L';
+		r.follow = 'L';
 		break;
 	default:
 		usage();
@@ -316,7 +318,7 @@ main(int argc, char *argv[])
 			tarfile = stdout;
 		}
 		chdir(dir);
-		c(argv[0], 0, NULL);
+		c(argv[0], NULL, &r);
 		break;
 	case 't':
 	case 'x':
@@ -342,5 +344,5 @@ main(int argc, char *argv[])
 		break;
 	}
 
-	return 0;
+	return recurse_status;
 }