* optabs.h (enum optab_index): Add new OTI_pow and OTI_atan2.
	(pow_optab, atan2_optab): Define corresponding macros.
	* optabs.c (init_optabs): Initialize pow_optab and atan2_optab.
	* genopinit.c (optabs): Implement pow_optab and atan2_optab
	using pow?f3 and atan2?f3 patterns.
	* builtins.c (expand_errno_check): New function to update errno
	if necessary, split out from expand_builtin_mathfn.
	(expand_builtin_mathfn): Use expand_errno_check.
	(expand_builtin_mathfn_2): New function to handle expanding binary
	math functions, reusing the code in expand_errno_check.
	(expand_builtin): Handle the pow and atan2 math built-ins,
	BUILT_IN_{POW,POWF,POWL,ATAN2,ATAN2F,ATAN2L} via the new function
	expand_builtin_mathfn_2.

	* doc/md.texi: Document new pow?f3 and atan2?f3 patterns.

From-SVN: r62708