Weston 1.8.0 was released on June 2, 2015.
libinput changed ABI so the old weston doesn't run. Increase the release to make a new build with the new libinput happen.
This package builds weston with the Raspberry Pi compositor on armv7h too. As a matter of fact the weston package from community only support the Raspberry Pi armv6h models, hence this package is needed for proper Raspberry Pi 2 support.