isl_map_transitive_closure: construct paths that can be composed
isl_map_transitive_closure: construct paths that can be composed

In particular, keep track of the number of steps in an extra
coordinates such that composition simply sums the number of steps.

jleben/isl,serge-sans-paille/isl,BobSaget-Mod/libisl,KangDroidSMProject/ISL,Meinersbur/isl,serge-sans-paille/isl,cfx-next/toolchain_isl-upstream,cfx-next/toolchain_isl-upstream,epowers/isl,nicolasvasilache/isl,PollyLabs/isl,inducer/isl-mirror,Distrotech/isl,jleben/isl,nicolasvasilache/isl,simbuerg/isl,SaberMod/isl-current,PollyLabs/isl,PollyLabs/isl,jleben/isl,UBERTC/isl,jleben/isl,cfx-next/toolchain_isl-upstream,Meinersbur/isl,PollyLabs/isl,epowers/isl,SaberMod/isl-current,BenzoSM/isl,BenzoSM/isl,PollyLabs/isl,BenzoSM/isl,evaautomation/isl,epowers/isl,abduld/isl,cfx-next/toolchain_isl-upstream,evaautomation/isl,UBERTC/isl,pierrotdelalune/isl,inducer/isl-mirror,Distrotech/isl,BobSaget-Mod/libisl,UBERTC/isl,Distrotech/isl,BobSaget-Mod/libisl,VanirLLVM/toolchain_isl,abduld/isl,nicolasvasilache/isl,abduld/isl,serge-sans-paille/isl,VanirLLVM/toolchain_isl,BenzoSM/isl,Meinersbur/isl,evaautomation/isl,tobig/isl,SaberMod/isl-current,VanirLLVM/toolchain_isl,inducer/isl-mirror,KangDroidSMProject/ISL,simbuerg/isl,serge-sans-paille/isl,evaautomation/isl,BobSaget-Mod/libisl,UBERTC/isl,tobig/isl,simbuerg/isl,crossbuild/isl,KangDroidSMProject/ISL,abduld/isl,VanirLLVM/toolchain_isl,pierrotdelalune/isl,epowers/isl,nicolasvasilache/isl,VanirLLVM/toolchain_isl,inducer/isl-mirror,pierrotdelalune/isl,BobSaget-Mod/libisl,KangDroidSMProject/ISL,tobig/isl,Meinersbur/isl,nicolasvasilache/isl,epowers/isl,simbuerg/isl,pierrotdelalune/isl,cfx-next/toolchain_isl-upstream,jleben/isl,simbuerg/isl,Distrotech/isl,Distrotech/isl,crossbuild/isl,crossbuild/isl,pierrotdelalune/isl,tobig/isl,KangDroidSMProject/ISL,inducer/isl-mirror,BenzoSM/isl,crossbuild/isl,serge-sans-paille/isl,SaberMod/isl-current