fix datatype mismatch warnings
fix some datatype mismatches in ext/bz2

Additionally, as bz2 read/write routines expect int for sizes, it could
overflow. So fixed the logic. Things in compress/decompress are more
complicated so they was left as they are yet.
fix datatype mismatch warnings
fix datatype mismatch warnings
fix datatype mismatches
fix datatype mismatche warnings
fix datatype mismatches