d: Give the result of evaluated expressions a location

d: Give the result of evaluated expressions a location

CST trees that were converted back to a D front-end AST node lost all
location information of the original expression.  Now this is propagated
on to the literal expression.

gcc/d/ChangeLog:

	* d-tree.h (d_eval_constant_expression): Add location argument.
	* d-builtins.cc (d_eval_constant_expression): Give generated constants
	a proper file location.
	* d-compiler.cc (Compiler::paintAsType): Pass expression location to
	d_eval_constant_expression.
	* d-frontend.cc (eval_builtin): Likewise.