doc: update isl_pw_qpolynomial_gist description
doc: update isl_pw_qpolynomial_gist description

In particular, update the description to changes made in 661c374
(isl_pw_qpolynomial_gist: also try to eliminate integer divisions,
Fri Nov 5 16:44:54 2010 +0100).

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

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