Ali Sallabi, left, a Libyan, and Abdel Moneim Abou el-Fotouh, an Egyptian, say their states should blend Islam and modernity.Credit...Left, Moises Saman for The New York Times; right, Khaled Desouki/A.F.P. — Getty Images CAIRO — By force of this year’s Arab revolts and revolutions, activists marching under the banner of Islam are on the verge of a reckoning decades in the making: the prospect of a