backport: re PR target/61055 ([avr] wrong test instruction after increment with -O1)

backport: re PR target/61055 ([avr] wrong test instruction after increment with -O1)

gcc/
	Backport from 2014-05-09 trunk r210267
	PR target/61055
	* config/avr/avr.md (cc): Add new attribute set_vzn.
	(addqi3, negqi2) [cc]:
	Set cc insn attribute to set_vzn instead of set_zn for alternatives
	with INC, DEC or NEG.
	* config/avr/avr.c (avr_notice_update_cc): Handle SET_VZN.
	(avr_out_plus_1): ADIW sets cc0 to CC_SET_CZN.
	INC, DEC set cc0 to CC_CLOBBER.

gcc/testsuite/
	Backport from 2014-05-09 trunk r210267
	PR target/61055
	* gcc.target/avr/torture/pr61055.c: New test.

From-SVN: r210270