Compressing small files increases archive size

[d-divita]

Select your issue type: (check at least one)

• [x] Bug
• [ ] Question
• [ ] Suggestion
• [ ] Other (please describe):

Describe your issue: When compressing small files, for example a bunch of small .txt files, the resulting archive is bigger than the files it contains.

Ways to Reproduce the issue (optional):

1. Create a .txt file with a few words in it (it will be some bytes in size)
2. Compress it via QArchive
3. The resulting archive is about 10KB (tested with ZipFormat, SevenZipFormat, TarFormat)