128 KiB DSC files ought to be enough for everyone

128 KiB DSC files ought to be enough for everyone

Your mileage may vary, but don't worry: There is more than one way to
do it, but our one size fits all is not a bigger hammer, but an entire
roundhouse kick! So brace yourself for the tl;dr: The limit is gone.*

Beware: This fixes also the problem that a double newline is
unconditionally added 'later' which is an overcommitment in case
the dsc filesize is limit-2 <= x <= limit.

* limited to numbers fitting into an unsigned long long.

Closes: 774893