isl_map_read: extract out read_var_def
isl_map_read: extract out read_var_def

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

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