Fixed salut initialization to use a callback and not calling code that is in salut core and not in the plugin code
This follows changes made in telepathy salut plugin library, in https://bugs.freedesktop.org/show_bug.cgi?id=45716
The branch is in http://cgit.collabora.com/git/user/asoliver/ytstenut-plugins/log/?h=standalone-salut-plugin
Updated branch in URL following my latest changes for bug 45716.
Also takes out the non-portable linker flags we used to temporarily simulate on Linux how the plugin would be compiled on Windows and similar targets, included in Alvaro's branch.
I'll merge this when the branch for bug 45716 gets through - consider the fundamental matter from Alvaro review+d by me.
The dep branch has been merged, so I merged this as well. I tested that the latest state of both work together.