- remove zero size files on I-M-S hit
* methods/https.cc:
- only send LastModified if we actually have one
- send range request with if-range
- delete failed downloads
- only send i-m-s if last-modified is > 0
- instead of resume send a range: if-range: custom header
- merge 304 detection patch from thom may (thanks!)
* apt-pkg/acquire-item.cc:
- remove empty files on i-m-s hits from partial/