<rdar://problem/13069948>

Major fixed to allow reading files that are over 4GB. The main problems were that the DataExtractor was using 32 bit offsets as a data cursor, and since we mmap all of our object files we could run into cases where if we had a very large core file that was over 4GB, we were running into the 4GB boundary.

So I defined a new "lldb::offset_t" which should be used for all file offsets.

After making this change, I enabled warnings for data loss and for enexpected implicit conversions temporarily and found a ton of things that I fixed.

Any functions that take an index internally, should use "size_t" for any indexes and also should return "size_t" for any sizes of collections.