[libvirt] libvirt 0.5.1 tag missing in git repo: just applied manually

[Jim Meyering <jim meyering net>]

FYI,

Itamar Heim noticed that the LIBVIRT_0_5_1 tag, while in CVS, was not
in the git repository (thanks, Itamar).

I have a vague recollection that git cvsimport creates certain tags lazily
(like only once there is something on a branch) but I have manually
applied and pushed this particular tag, nonetheless.