* real.c (real_copysign): New function to implement libm's copysign.
	* real.h (real_copysign): Prototype here.
	* fold-const.c (tree_expr_nonnegative_p): The result of sqrt, sqrtf
	and sqrtl can be negative, as sqrt(-0.0) = -0.0.  Correct whitespace.
	* builtins.c (fold_builtin_isascii, fold_builtin_toascii,
	fold_builtin_isdigit): Add function prototypes.
	(fold_builtin_copysign): New function to fold copysign, copysignf
	and copysignl.  Optimize copysign(x,x) as x.  Evaluate copysign of
	constant arguments at compile-time using real_copysign.  Fold
	copysign(X,Y) as fabs(X) if Y is always non-negative.
	(fold_builtin_1): Correct minor whitespace/style issues.  Call
	fold_builtin_copysign for BUILT_IN_COPYSIGN{,F,L}.

	* gcc.dg/builtins-41.c: New test case.
	* gcc.dg/builtins-42.c: New test case.

From-SVN: r82721