Poland's Kaczynski backs deal with Cameron to keep Britain in EU

By Adrian Krajewski and William James WARSAW/COPENHAGEN (Reuters) - Prime Minister David Cameron secured the support of Poland's most powerful man on Friday for a proposed deal to keep Britain in the European Union, though an opinion poll suggested voters may still reject continued membership in a planned referendum. To win a vote expected in June on staying in the EU, Cameron says he needs a pact to curb benefits for new migrant workers from EU countries, an opt-out from moves towards political