[Merge] ~mitya57/compiz:lp1882792 into compiz:master

[Dmitry Shachnev]

Alberts: I removed all uses of SKIP_UNITY_BUILD_INCLUSION except two:

- outputdevices_x11.cpp had some strange linker errors when using Unity build, see the commit message.
- gsettings_util.c, that file redefined CCS_LOG_DOMAIN so it needed to be built separately in order for log functions to work.
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https://code.launchpad.net/~mitya57/compiz/+git/compiz/+merge/388842
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