IMPORT: slz: fix the adler32 accumulators signedness on 32-bit

IMPORT: slz: fix the adler32 accumulators signedness on 32-bit

slz_adler32_block() unfortunately uses a signed long as the crc accumulator
instead of an unsigned one, meaning that for CRC values where the 32th bit
is set on 32-bit machines, the right shift will drag sign bits and corrupt
it. This only affects zlib streams on 32-bit systems (rfc1950) and has
been there for a very long time, showing that the zlib format is really
not much used in target environments.

The fix is trivial, just change the accumulators to unsigned long.

This is libslz upstream commit 912a707525fd2d6a63c9884ef02f69e7379c304c