cloog_loop_separate: combine loops with identical domains first
cloog_loop_separate: combine loops with identical domains first

By combining loops with identical domains before actually performing
the separation, we can avoid performing some duplicate domain operations.

Signed-off-by: Sven Verdoolaege <e5350bbed4977f5eb8ae1dc6abd9ae59d21ace75@kotnet.org>

evaautomation/cloog,Distrotech/cloog,UBERTC/cloog,periscop/cloog,cfx-next/toolchain_cloog-upstream,Syllo/cloog,VanirLLVM/toolchain_cloog,SaberMod/cloog-current,VanirLLVM/toolchain_cloog,Distrotech/cloog,evaautomation/cloog,cfx-next/toolchain_cloog-upstream,cfx-next/toolchain_cloog-upstream,epowers/cloog,heysion/cloog-clone,epowers/cloog,Syllo/cloog,SaberMod/cloog-current,VanirLLVM/toolchain_cloog,Distrotech/cloog,periscop/cloog,UBERTC/cloog,UBERTC/cloog,heysion/cloog-clone,heysion/cloog-clone,epowers/cloog