busybox

tr: fix overflow in expand and complement, fix stop after [:class:],
 fix order of [:xdigit:], make tr require one param at least.

function                                             old     new   delta
expand                                              1743    1849    +106
tr_main                                              463     518     +55
complement                                            72      75      +3
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(add/remove: 0/0 grow/shrink: 3/0 up/down: 164/0)             Total: 164 bytes