d: Use new isXxxxExp helpers where possible

d: Use new isXxxxExp helpers where possible

gcc/d/ChangeLog:

	* d-attribs.cc (build_attributes): Use isXxxxExp helpers instead of
	explicit casts.
	* d-codegen.cc (d_build_call): Likewise.
	* d-compiler.cc (Compiler::paintAsType): Likewise.
	* decl.cc (ExprVisitor::visit): Likewise.
	(layout_class_initializer): Likewise.
	* expr.cc (ExprVisitor::lvalue_p): Likewise
	(ExprVisitor::visit): Likewise.
	* types.cc (layout_aggregate_members): Likewise.