tree-optimization/116796 - virtual LC SSA broken after unrolling

When the unroller unloops loops it tracks whether it changes any
nesting relationship of remaining loops but when scanning a loops
preheader it fails to pass down the LC-SSA-invalidated bitmap, losing
the fact that an unrolled formerly inner loop can now be placed on
an exit of its outer loop.  The following fixes that.

	PR tree-optimization/116796
	* cfgloopmanip.cc (fix_loop_placements): Get LC-SSA-invalidated
	bitmap and pass it on.
	(remove_path): Pass LC-SSA-invalidated to fix_loop_placements.