Zero-initialize LZSS' cyclic buffer.

This fixes the random character issue in the decompression of the first
game's CIFLIST file, caused by the run info towards the beginning of the
file accessing as-yet unfilled parts of the buffer.

This hopefully 100% correct fix relies on three reasonable assumptions:

 - Her's compressor did not mis-write the offset into the cyclic buffer;
 - Zero is a reasonable start state to set your buffer to; and
 - The resulting CIFLIST, separating fields in each row with a series of
   null characters, is correct.

I'm not 100% sure on this (for instance, nulls appear in a comment line
of the CIFLIST where they don't make sense). The nulls in this instance
are possibly supposed to be something else, likely TAB. We won't know
for sure unless & until someone finds the decompressor in Her's code and
discovers what the initial state of the buffer is.

At the very least, decompressing a file multiple times won't result in
different output anymore. Only two files in the first game's CIFLIST
showed varying data before; and only CIFLIST changed every time. So
hopefully there won't be too many files affected if a default of ^@
turns out to be horribly wrong.