- used new get_Block_cfgpred_block() function instead of get_nodes_block(get_Block_cf...

- used new get_Block_cfgpred_block() function instead of get_nodes_block(get_Block_cfgpred(n, 0))
- when getting a block from previous control flow, always skip Proj nodes
- equivalent_node_Add/Sub  check that the modes match before returning a predecessor
- use get_irn_n(*, -1) instead of get_nodes_block() to place a node into the same block as another one
- check that the graph is pinned before using block info for decisions
- removed nodes in dead blocks from keep-alive if possible

[r6143]