Support > 2GiB seeks in adb_lseek.

Also stop using size_t (which will be 32-bit on Win32) for offsets in
adb_sideload_host, and stop truncating large file sizes in our
"sideload-host" messages.

Bug: http://b/112003354
Test: builds
Change-Id: If5b7cc9d1fc7ff7ca6eaebd20418f7b061846203