[PATCH] fix lots of warnings about 'struct tty_driver'

When compiling 2.5.20 (and ealier, likely) without procfs, the declaration
for struct tty_driver is missing in proc_fs.h, causing many compiler warnings
that are fixed by this patch.

include/linux/proc_fs.h

@@ -198,6 +198,7 @@ static inline struct proc_dir_entry *create_proc_info_entry(const char *name,
 	mode_t mode, struct proc_dir_entry *base, get_info_t *get_info)
 	{ return NULL; }
 
+struct tty_driver;
 static inline void proc_tty_register_driver(struct tty_driver *driver) {};
 static inline void proc_tty_unregister_driver(struct tty_driver *driver) {};