reimplement isl_stream_read_aff in terms of isl_stream_read_multi_aff
reimplement isl_stream_read_aff in terms of isl_stream_read_multi_aff

Reading an isl_aff is essentially a special case of reading an isl_multi_aff.
We therefore do not need any special code for reading an isl_aff, but can
instead read it as an isl_multi_aff and then extract out the isl_aff.

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

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