doc: add a note on isl_dim_type
doc: add a note on isl_dim_type

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

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