[libvirt] Add patches to allow users to join running containers.

[PATCH 1/2] Add virGetUserDirectoryByUID to retrieve users homedir [PATCH 2/2] virt-login-shell joins users into lxc container. This patch implements most of the changes suggested by Dan Berrange and Eric Blake. Some replies to suggested changes. Removed mingw-libvirt.spec.in changes since virt lxc probably can not be supported in Windows. Not sure if I need to make changes so my code will not build on that platform. Did not make the changes to install virt-login-shell as 4755 automatically. I guess I want a more firm, make that change request... I did not make a helper function to parse a list of strings out of conf file. The getuid and getgid calls return the user that executed the program, when the app is setuid geteuid and getegid return "0". I believe getuid and getgid are correct. Added virt-login-shell --help, not sure what --program would do? The program is hard coded to LXC because there is no way that I know of for a ZZ process to join a running qemu instance. I have heard back from one security review from Miloslav Trmac, who had similar comments as Eric.