Bug#831436: liquidwar: Please update build-depends on liballegro4-dev

[Jeremy Bicha]

Source: liquidwar
Version: 5.6.4-4

Please build-depend on liballegro4-dev instead of the virtual package
liballegro4.2-dev.

allegro4.2 was replaced a while ago by allegro4.4.

This change was made in Ubuntu:
https://launchpadlibrarian.net/144272350/liquidwar_5.6.4-3build1_5.6.4-3ubuntu1.diff.gz

Thanks,
Jeremy Bicha