HAVANA (Reuters) – Cubans headed to the polls on Sunday to vote on a package of measures that would upend the island’s long-held “machista” culture and legalize gay marriage even as the country wrestles with a deepening economic crisis. If approved, the 100-page “family code” would put Cuba at the vanguard of progressive social policy in Latin America, legalizing same-sex marriage and civil unions, allowing same-sex couples to adopt children, and promoting equal sharing of domestic rights and responsibilities between men and women. President Miguel Diaz-Canel, who walked with his wife to vote …