re PR debug/48343 (ICE compiling i586 linux-2.6.38/drivers/staging/wlan-ng/p80211wep.c: in form_sum, at reload.c:5338)

	PR debug/48343
	* combine.c (combine_instructions): Add last_combined_insn,
	update it if insn is after it, pass it to all try_combine
	calls.
	(try_combine): Add last_combined_insn parameter, pass it instead of
	i3 to propagate_for_debug.

	* gcc.dg/torture/pr48343.c: New test.

From-SVN: r172109