cloog_loop_specialize: only specialize with convex domain
cloog_loop_specialize: only specialize with convex domain

It the result of projecting the inner domain somehow ends up
being non-convex, which may happen if existentially quantified
variable definitions need to be recomputed, then skip the specialization
for the domain at hand.

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

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