builtins.c (fold_builtin_exponent): Evaluate constant arguments at compile-time using...

builtins.c (fold_builtin_exponent): Evaluate constant arguments at compile-time using MPFR.

	* builtins.c (fold_builtin_exponent): Evaluate constant arguments
	at compile-time using MPFR.  Change parameter VALUE to FUNC,
	update all callers.
	(do_mpfr_arg1): Rename `exact' to `inexact'.  Carefully check
	for overflow and underflow at all times and avoid folding in
	those cases.

From-SVN: r117995