The "multiple plugins loaded at once" strategy was always a big fiction:
while it may be viable if you're super careful, it's fragile and requires
a bit of infrastructure that we would be better off without.
Note that for simplicity, we're keeping the MetaPluginManager, but it only
manages one plugin. A possible future cleanup would be to remove it entirely.
https://bugzilla.gnome.org/show_bug.cgi?id=676855
If mutter is going to be a "real" library, then it should install its
includes so that users can do
#include <meta/display.h>
rather than
#include <display.h>
So rename the includedir accordingly, move src/include to src/meta,
and fix up all internal references.
There were a handful of header files in src/include that were not
installed; this appears to have been part of a plan to keep core/,
ui/, and compositor/ from looking at each others' private includes,
but that wasn't really working anyway. So move all non-installed
headers back into core/ or ui/.
https://bugzilla.gnome.org/show_bug.cgi?id=643959
Move all of the mutter code into a new libmutter-wm.so, split its
main() method into meta_get_option_context(), meta_init() and
meta_run(), add methods for using in-process plugins, and add
libmutter-wm.pc pointing to the new library.
The mutter binary is now just a tiny program that links against
libmutter-wm. The --version and --mutter-plugins options are handled
at the mutter level, not in libmutter-wm, and a few strange unused
command-line options (--no-force-fullscreen and --no-tab-popup) have
been removed.
https://bugzilla.gnome.org/show_bug.cgi?id=643959
