[PATCH](or feature-request) build both systemd and ck versions

[Luke T. Shumaker <lukeshu sbcglobal net>]

I propose that the build system should generage both
`NetworkManager-ck' and `NetworkManager-systemd' binaries and symlink
`NetworkManager' to one of them.

This way a distro that supports both sysvinit and systemd (such as
Arch) can easily offer both.  In the case of Arch, the correct version
can be decided by symlinking `NetworkManager'->`NetworkManager-ck'
(for compatability) and modifying the systemd `NetworkManager.service'
file to run `NetworkManager-systemd' instead of just `NetworkManager'.

The attached patch modifies `configure.ac', `src/Makefile.am', and
`data/NetworkManager.service.in' to do just that; however, does NOT
patch anything to create a symlink.

Happy hacking!
~ Luke Shumaker