Revert r28379.
Revert r28379.

This optimization is unsafe and breaks Load-Store-optimization.

It is not enough that both loads are connected by the memory edge,
if one Load has an exception-edge, they cannot be parallelized, because
this would destroy exception order.
load-store-opt handle this case and many others, but expect all
Loads in order yet.
opt_parallelize_mem() does this optimization in a wider range.

[r28385]

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