* fold-const.c (fold):  Use "fold" following build in more places.
	Optimize sqrt(x)*sqrt(x) as x, pow(x,y)*pow(z,y) as pow(x*z,y),
	pow(x,y)*pow(x,z) as pow(x,y+z) and x/pow(y,z) as x*pow(y,-z).

	* gcc.dg/builtins-11.c: New test case.

From-SVN: r65387