tree-optimization/113373 - add missing LC PHIs for live operations

tree-optimization/113373 - add missing LC PHIs for live operations

The following makes reduction epilogue code generation happy by properly
adding LC PHIs to the exit blocks for multiple exit vectorized loops.

Some refactoring might make the flow easier to follow but I've refrained
from doing that with this patch.

I've kept some fixes in reduction epilogue generation from the earlier
attempt fixing this PR.

	PR tree-optimization/113373
	* tree-vect-loop-manip.cc (slpeel_tree_duplicate_loop_to_edge_cfg):
	Create LC PHIs in the exit blocks where necessary.
	* tree-vect-loop.cc (vectorizable_live_operation): Do not try
	to handle missing LC PHIs.
	(find_connected_edge): Remove.
	(vect_create_epilog_for_reduction): Cleanup use of auto_vec.

	* gcc.dg/vect/vect-early-break_104-pr113373.c: New testcase.