re PR target/10979 (ICE in subst_stack_regs_pat with -O -ffast-math and atan2)

	PR target/10979
	* config/i386/i386.md (atan2df3, atan2sf3, atan2xf3, atan2tf3):
	Changed to define_expand patterns that copy operand[1] to prevent
	it from being clobbered before emitting an atan2?f3_1 insn.
	(atan2df3_1, atan2sf3_1, atan2xf_1, atan2tf3_1): New define_insn
	patterns that actually specify the behaviour of x87's FPATAN.

	* gcc.dg/20030707-1.c: New testcase.

From-SVN: r69060