* devpts "upcalls" eliminated.
	* instead of playing games with revalidation we simply use
ramfs-style tree and kill dentries upon devpts_pty_kill().  That
allows to get rid of a lot of code in fs/devpts/*.c.
	* devpts_fs.h cleaned up.
	* devpts/root.c and devpts/devpts_i.h removed.
	* array of pointers to devpts inodes killed; with ramfs-style tree
it's not needed anymore.
	* devpts/inode.c cleaned up.
	* devpts_pty_new() used to get mk_kdev() only to convert it to
dev_t (hardly a surprise, since it's mknod() in disguise).  Now it gets
dev_t as an argument.