IMPALA-1116: Codec interface support for large files/buffers.

The current codec interface does not support large files/buffers as the lengths are
passed as ints (int32_t). This changes either uses int64_t or calls a safe(r) version
of ProcessBlock() that checks for overflows.

Change-Id: I5820a707f1e11e7a617609d0956bb9a89e3c02ad