Replaced set_irn_n(*, -1, *) and get_irn_n(*, -1) by new get_nodes_block()/set_nodes_...

Replaced set_irn_n(*, -1, *) and get_irn_n(*, -1) by new get_nodes_block()/set_nodes_block() implementation
caveats:
 - the old outs do not see the anchor node yet
 - the new edges wrongly use get_irn_n(*, -1)
 - the new edges do not realize that the move of a node moves all its Projs
 - the anchor node still must have the -1 input set (due to edges bug...)

[r15135]