Fixed remove_critical_cf_edges():  - use irg_block_walk_graph() to speed up  - build block only at critical edges: curretn block has more than 1 predecessor   and the predecessor is a forking op  - ignore ALL exception edges
Fixed remove_critical_cf_edges():
 - use irg_block_walk_graph() to speed up
 - build block only at critical edges: curretn block has more than 1 predecessor
  and the predecessor is a forking op
 - ignore ALL exception edges

[r8294]

killbug2004/libfirm,killbug2004/libfirm,8l/libfirm,8l/libfirm,libfirm/libfirm,jonashaag/libfirm,killbug2004/libfirm,MatzeB/libfirm,davidgiven/libfirm,8l/libfirm,killbug2004/libfirm,jonashaag/libfirm,8l/libfirm,davidgiven/libfirm,jonashaag/libfirm,8l/libfirm,davidgiven/libfirm,killbug2004/libfirm,MatzeB/libfirm,davidgiven/libfirm,killbug2004/libfirm,MatzeB/libfirm,8l/libfirm,MatzeB/libfirm,libfirm/libfirm,libfirm/libfirm,MatzeB/libfirm,jonashaag/libfirm,killbug2004/libfirm,jonashaag/libfirm,libfirm/libfirm,8l/libfirm,davidgiven/libfirm,MatzeB/libfirm,jonashaag/libfirm,libfirm/libfirm,davidgiven/libfirm,jonashaag/libfirm,MatzeB/libfirm,davidgiven/libfirm