Defines starting with `b' in kern

• BOTH kern/tty.c:1821
• BQ_AGE kern/vfs_bio.c:43
• BQ_EMPTY kern/vfs_bio.c:44
• BQ_LOCKED kern/vfs_bio.c:41
• BQ_LRU kern/vfs_bio.c:42
• BQUEUES kern/vfs_bio.c:39
• BS kern/tty.c:86
• BUFSIZ kern/tty_pty.c:58