bitrot and linkat() fixes for Darwin.

ChangeLog.txt

@@ -6,6 +6,8 @@
           the documentation and behavior of link(2) to reflect host
           OS semantics: Linux will hardlink symlinks, Darwin will only
           hardlink their targets.
+	* (seebs) make linkat() implementation compile/run on Darwin,
+	  fix header bitrot for Mountain Lion.
 
 2012-08-09:
 	* (seebs) base_stat should be real_stat64, not stat64

ports/darwin/wrapfuncs.in

@@ -17,7 +17,7 @@ int setxattr(const char *pathname, const char *name, const void *value, size_t s
 int fsetxattr(int filedes, const char *name, const void *value, size_t size, u_int32_t position, int options);
 # local color UIDs
 int getgrouplist(const char *name, int basegid, int *groups, int *ngroups);
-int scandir(const char *path, struct dirent ***namelist, int (*filter)(struct dirent *), int (*compar)());
+int scandir(const char *path, struct dirent ***namelist, int (*filter)(const struct dirent *), int (*compar)());
 int getgroups(int size, gid_t *list);
 int fgetgrent_r(FILE *fp, struct group *gbuf, char *buf, size_t buflen, struct group **gbufp); /* real_func=pseudo_fgetgrent_r */
 int fgetpwent_r(FILE *fp, struct passwd *pbuf, char *buf, size_t buflen, struct passwd **pbufp); /* real_func=pseudo_fgetpwent_r */

pseudo.h

@@ -93,14 +93,15 @@ extern char *pseudo_version;
  * terms of each other, and for instance, open(...) is the same as
  * openat(AT_FDCWD, ...).  If no AT_FDCWD is provided, any value that can't
  * be a valid file descriptor will do.  Using -2 because -1 could be
- * mistaken for a failed syscall return.  Similarly, any value which isn't
- * zero will do to fake AT_SYMLINK_NOFOLLOW.  Finally, if this happened,
- * we set our own flag we can use to indicate that dummy implementations
- * of the _at functions are needed.
+ * mistaken for a failed syscall return.  AT_SYMLINK_NOFOLLOW has to be
+ * non-zero; AT_SYMLINK_FOLLOW has to be non-zero and different.  Finally,
+ * if this happened, we set our own flag we can use to indicate that dummy
+ * implementations of the _at functions are needed.
  */
 #ifndef AT_FDCWD
 #define AT_FDCWD -2
 #define AT_SYMLINK_NOFOLLOW 1
+#define AT_SYMLINK_FOLLOW 2
 #define PSEUDO_NO_REAL_AT_FUNCTIONS
 #endif