tree-optimization/106521 - unroll-and-jam LC SSA rewrite

The LC SSA rewrite performs SSA verification at start but the VN
run performed on the unrolled-and-jammed body can leave us with
invalid SSA form until CFG cleanup is run.  So make sure we do that
before rewriting into LC SSA.

	PR tree-optimization/106521
	* gimple-loop-jam.cc (tree_loop_unroll_and_jam): Perform
	CFG cleanup manually before rewriting into LC SSA.

	* gcc.dg/torture/pr106521.c: New testcase.