re PR rtl-optimization/55006 (aermod.f90 is miscompiled with '-m64 -O2 -funroll-loops' after revision 192526)

	PR rtl-optimization/55006
	* loop-unroll.c (struct iv_to_split): Add new 'orig_var' member.
	(analyze_iv_to_split_insn): Record it.
	(maybe_strip_eq_note_for_split_iv): New function to remove REG_EQUAL
	notes that refer to IVs that are being split.
	(apply_opt_in_copies): Use maybe_strip_eq_note_for_split_iv.  Twice.
	Use FOR_BB_INSNS_SAFE.

From-SVN: r193876