mx.pc: Update the Requires field
mx.pc: Update the Requires field

Mx depends on clutter-x11-1.0 for the clutter_x11_* API.

clutter-project/mx,jonnylamb/mx,clutter-project/mx,jonnylamb/mx,pwithnall/mx,jonnylamb/mx,pwithnall/mx,pwithnall/mx,clutter-project/mx,clutter-project/mx,pwithnall/mx,jonnylamb/mx