Releasing Gammu

1. Ensure that all tests pass on both Linux and Windows.

2. Update changelog and fill in release date in ChangeLog.

3. Update man pages using make update-man.

4. Run ./admin/make-release to verify release build works.

5. (optional) Test created tarballs.

6. Run ./admin/make-release branch to make final release.

7. Push created tag to GitHub.

8. Wait for AppVeyor to produce Windows binaries.

9. Import release to the website.