community/dar: upgrade to 2.7.4
from 2.7.3 to 2.7.4
- fixed excessive context control that led libdar to report a bug when an file-system I/O error was returned by the operating system
- fixed min-digits auto-detection, which only worked when slice number 1 was present, even if subsequent slices could be used to detect its value
- fixed typos and minor incoherence in documentation
- update version information to display libthreadar barrier implementation used, info available since its release 1.4.0