Handle T message and prepare for adding -p option

previous version would 'sanity' check with permission 0777 only,
we now check whether the permissions correspond with the file on the
remote server.

…10, 64) (#87)

This change solves a problem on 32-bit systems where file sizes larger than 2^32 could not be parsed. By using ParseInt directly and setting the bit-size to 64 explicitly, the size is always parsed and stored as a 64-bit integer regardless of the host platform.