When using an app from the Arch repositories, there is a function to add a screenshotter to the panel. The git version doesn't have this feature anymore, so I can't check if it's a bug after your patch.
Ahh, did you install screenshooter in your system but it doesn't appear in panel's plugins list? If so, that's probably because you didn't set the correct prefix, ./autogen.sh --prefix=/usr && make && sudo make install should fix your problem.