Using off_t, at least, in DiskAdaptor layer is problematic because
torrent can contain under 2GiB files but total sum of those files may
exceed 2GiB limit, which makes off_t overflow in 32 bit system without
large file support. So we use int64_t in API. We'll check the file
length before download so that it does not exceed max off_t.
Added .cc file for classes/structs that only provided by header
file. Defined non-POD classes' ctor, dtor in .cc file. Moved
implementation code in header file to .cc file for major
classes/strucsts.
Implemented BitTorrent/http/ftp integrated download.
I've rewritten lots of files and now some headers have forward
class declarations to reduce compile time.
The implementation is extremely alpha stage, I recommend to use this
for testing purpose only.