* real.c (real_powi): New function to calculate the value of
	a real raised to an integer power, i.e. pow(x,n) for int n.
	(real_sqrt): Convert to using the faster do_add, do_multiply
	and do_divide API for consistency with the rest of real.c.
	* real.h (real_powi): Prototype here.
	* builtins.c (fold_builtin):  Avoid local variable mode when
	evaluating sqrt at compile time.  Attempt to evaluate pow at
	compile-time, by checking for an integral exponent.

	* gcc.dg/builtins-14.c: New test case.

From-SVN: r66515