PR middle-end/30789

	* builtins.c (do_mpc_arg2): Make extern, define for any MPC
	version.  Move declaration...
	* real.h (do_mpc_arg2): ... here.
	* fold-const.c (const_binop): Use MPC for complex MULT_EXPR
	and RDIV_EXPR.

testsuite:
	* gcc.dg/torture/builtin-math-7.c: New.

From-SVN: r150760