* optabs.h (enum optab_index): Add new OTI_tan and OTI_atan.
	(tan_optab, atan_optab): Define corresponding macros.
	* optabs.c (init_optabs): Initialize tan_optab and atan_optab.
	* genopinit.c (optabs): Implement tan_optab and atan_optab
	using tan?f2 and atan?f2 patterns.
	* builtins.c (expand_builtin_mathfn): Handle BUILT_IN_TAN{,F,L}
	using tan_optab, and BUILT_IN_ATAN{,F,L} using atan_optab.
	Change the default value of errno_set to false.
	(expand_builtin): Expand BUILT_IN_TAN{,F,L} and BUILT_IN_ATAN{,F,L}
	using expand_builtin_mathfn.

	* config/i386/i386.md (atansf2, atandf2, atanxf2, atantf2): New
	expander patterns implemented using existing atan2?f3 patterns.

	* gcc.dg/i386-387-5.c: New test case.
	* gcc.dg/i386-387-6.c: New test case.
	* gcc.dg/builtins-23.c: New test case.

From-SVN: r68013