vfs/{b|btr|package|b}fs/ext2/exfat: common access check.

* Added VFS helper function check_access_permissions() that combines
  several partially correct versions to the one true version (tm).
* All but BFS (since recently) missed the S_IXOTH for root on directories,
  and all but packagefs missed proper group handling.

headers/os/drivers/fs_interface.h

@@ -1,10 +1,11 @@
 /*
- * Copyright 2004-2010, Haiku Inc. All Rights Reserved.
+ * Copyright 2004-2014, Haiku Inc. All Rights Reserved.
  * Distributed under the terms of the MIT License.
  */
 #ifndef _FS_INTERFACE_H
 #define _FS_INTERFACE_H
 
+
 /*! File System Interface Layer Definition */
 
 
@@ -330,6 +331,8 @@ extern status_t unremove_vnode(fs_volume* volume, ino_t vnodeID);
 extern status_t get_vnode_removed(fs_volume* volume, ino_t vnodeID,
 					bool* _removed);
 extern fs_volume* volume_for_vnode(fs_vnode* vnode);
+extern status_t check_access_permissions(int accessMode, mode_t mode,
+					gid_t nodeGroupID, uid_t nodeUserID);
 
 extern status_t read_pages(int fd, off_t pos, const struct iovec* vecs,
 					size_t count, size_t* _numBytes);