Update the pkg-config requires list
Update the pkg-config requires list

Clutter depends on various libraries, some of them backend-specific
like the X11 libraries.

Whenever possible, we should add those requirements to the pkg-config
file. For this reason, we have a variable inside the configure.ac
template file which should be filled with the backend-specific modules
we check for during configure time, and then added to the standard
list of dependencies that we write inside the clutter.pc file.

djdeath/clutter-multithreaded,GNOME/clutter,tardyp/clutter,djdeath/clutter-android,heysion/clutter-clone,kerrickstaley/clutter-vala,Distrotech/clutter,jigpu/clutter,jigpu/clutter,GNOME/clutter,collects/clutter,djdeath/clutter,djdeath/clutter-android,spatulasnout/clutter,rkudiyarov/clutter_osx,nobled/clutter,djdeath/clutter,ebassi/clutter,spatulasnout/clutter,kerrickstaley/clutter-vala,heysion/clutter-clone,djdeath/clutter,kerrickstaley/clutter-vala,collects/clutter,djdeath/clutter-multithreaded,jigpu/clutter,GNOME/clutter,Distrotech/clutter,spatulasnout/clutter,ebassi/clutter,ebassi/clutter,GNOME/clutter,djdeath/clutter,Distrotech/clutter,nobled/clutter,collects/clutter,jigpu/clutter,heysion/clutter-clone,djdeath/clutter-android,heysion/clutter-clone,collects/clutter,djdeath/clutter,tardyp/clutter,djdeath/clutter-android,spatulasnout/clutter,collects/clutter,ebassi/clutter,rkudiyarov/clutter_osx,rkudiyarov/clutter_osx,djdeath/clutter-multithreaded,tardyp/clutter,Distrotech/clutter,djdeath/clutter,GNOME/clutter,djdeath/clutter-multithreaded,jigpu/clutter,dlespiau/clutter,spatulasnout/clutter,dlespiau/clutter,nobled/clutter,Distrotech/clutter,jigpu/clutter,rkudiyarov/clutter_osx,djdeath/clutter-android,heysion/clutter-clone,dlespiau/clutter,kerrickstaley/clutter-vala,ebassi/clutter,Distrotech/clutter