Defines starting with `b' in kern

• BOTH kern/tty.c:1824
• BQ_AGE kern/vfs_bio.c:72
• BQ_EMPTY kern/vfs_bio.c:73
• BQ_LOCKED kern/vfs_bio.c:70
• BQ_LRU kern/vfs_bio.c:71
• BQUEUES kern/vfs_bio.c:68
• BS kern/tty.c:89
• BUFSIZ kern/tty_pty.c:58