Limit number of rewinds (#773)

This should reduce the number of timeouts. In case the decoder
keeps rewinding, check 4 of the 8 CRC8 bits. If they match, keep
rewinding.

With this approach, the fuzzer doesn't get 'faster' then plain
libFLAC, but fuzzing isn't affected too much by the CRC8 check.

Time will tell whether the fuzzer finds an input triggering
repeating rewinds, expensive processing ánd those 4 CRC8 bits
check out. If it finds such an input, more CRC8 bits need to be
checked.